diff --git a/core/core.services.yml b/core/core.services.yml
index 10d5121..7269288 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -1166,6 +1166,8 @@ services:
       - { name: twig.loader, priority: -100 }
   element_info:
     alias: plugin.manager.element_info
+  file.mime_type.mapper:
+    class: Drupal\Core\File\MimeType\MimeTypeMapper
   file.mime_type.guesser:
     class: Drupal\Core\File\MimeType\MimeTypeGuesser
     arguments: ['@stream_wrapper_manager']
@@ -1173,7 +1175,7 @@ services:
       - { name: service_collector, tag: mime_type_guesser, call: addGuesser }
   file.mime_type.guesser.extension:
     class: Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser
-    arguments: ['@module_handler']
+    arguments: ['@file.mime_type.mapper']
     tags:
       - { name: mime_type_guesser }
   file.mime_type.guesser.fileinfo:
diff --git a/core/lib/Drupal/Core/File/MimeType/ExtensionMimeTypeGuesser.php b/core/lib/Drupal/Core/File/MimeType/ExtensionMimeTypeGuesser.php
index dda1c4e..c6f5eaf 100644
--- a/core/lib/Drupal/Core/File/MimeType/ExtensionMimeTypeGuesser.php
+++ b/core/lib/Drupal/Core/File/MimeType/ExtensionMimeTypeGuesser.php
@@ -7,7 +7,6 @@
 
 namespace Drupal\Core\File\MimeType;
 
-use Drupal\Core\Extension\ModuleHandlerInterface;
 use Symfony\Component\HttpFoundation\File\MimeType\MimeTypeGuesserInterface;
 
 /**
@@ -16,858 +15,27 @@
 class ExtensionMimeTypeGuesser implements MimeTypeGuesserInterface {
 
   /**
-   * MIME extension mappings.
+   * The MIME type mapper to use for guessing.
    *
-   * @var array
-   *   Array of mimetypes correlated to the extensions that relate to them.
+   * @var MimeTypeMapperInterface
    */
-  protected $mapping = array(
-    'mimetypes' => array(
-      0 => 'application/andrew-inset',
-      1 => 'application/atom',
-      2 => 'application/atomcat+xml',
-      3 => 'application/atomserv+xml',
-      4 => 'application/cap',
-      5 => 'application/cu-seeme',
-      6 => 'application/dsptype',
-      350 => 'application/epub+zip',
-      7 => 'application/hta',
-      8 => 'application/java-archive',
-      9 => 'application/java-serialized-object',
-      10 => 'application/java-vm',
-      11 => 'application/mac-binhex40',
-      12 => 'application/mathematica',
-      13 => 'application/msaccess',
-      14 => 'application/msword',
-      15 => 'application/octet-stream',
-      16 => 'application/oda',
-      17 => 'application/ogg',
-      18 => 'application/pdf',
-      19 => 'application/pgp-keys',
-      20 => 'application/pgp-signature',
-      21 => 'application/pics-rules',
-      22 => 'application/postscript',
-      23 => 'application/rar',
-      24 => 'application/rdf+xml',
-      25 => 'application/rss+xml',
-      26 => 'application/rtf',
-      27 => 'application/smil',
-      349 => 'application/vnd.amazon.ebook',
-      28 => 'application/vnd.cinderella',
-      29 => 'application/vnd.google-earth.kml+xml',
-      30 => 'application/vnd.google-earth.kmz',
-      31 => 'application/vnd.mozilla.xul+xml',
-      32 => 'application/vnd.ms-excel',
-      33 => 'application/vnd.ms-excel.addin.macroEnabled.12',
-      34 => 'application/vnd.ms-excel.sheet.binary.macroEnabled.12',
-      35 => 'application/vnd.ms-excel.sheet.macroEnabled.12',
-      36 => 'application/vnd.ms-excel.template.macroEnabled.12',
-      37 => 'application/vnd.ms-pki.seccat',
-      38 => 'application/vnd.ms-pki.stl',
-      39 => 'application/vnd.ms-powerpoint',
-      40 => 'application/vnd.ms-powerpoint.addin.macroEnabled.12',
-      41 => 'application/vnd.ms-powerpoint.presentation.macroEnabled.12',
-      42 => 'application/vnd.ms-powerpoint.slideshow.macroEnabled.12',
-      43 => 'application/vnd.ms-powerpoint.template.macroEnabled.12',
-      44 => 'application/vnd.ms-word.document.macroEnabled.12',
-      45 => 'application/vnd.ms-word.template.macroEnabled.12',
-      46 => 'application/vnd.ms-xpsdocument',
-      47 => 'application/vnd.oasis.opendocument.chart',
-      48 => 'application/vnd.oasis.opendocument.database',
-      49 => 'application/vnd.oasis.opendocument.formula',
-      50 => 'application/vnd.oasis.opendocument.graphics',
-      51 => 'application/vnd.oasis.opendocument.graphics-template',
-      52 => 'application/vnd.oasis.opendocument.image',
-      53 => 'application/vnd.oasis.opendocument.presentation',
-      54 => 'application/vnd.oasis.opendocument.presentation-template',
-      55 => 'application/vnd.oasis.opendocument.spreadsheet',
-      56 => 'application/vnd.oasis.opendocument.spreadsheet-template',
-      57 => 'application/vnd.oasis.opendocument.text',
-      58 => 'application/vnd.oasis.opendocument.text-master',
-      59 => 'application/vnd.oasis.opendocument.text-template',
-      60 => 'application/vnd.oasis.opendocument.text-web',
-      61 => 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
-      62 => 'application/vnd.openxmlformats-officedocument.presentationml.slideshow',
-      63 => 'application/vnd.openxmlformats-officedocument.presentationml.template',
-      64 => 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
-      65 => 'application/vnd.openxmlformats-officedocument.spreadsheetml.template',
-      66 => 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
-      67 => 'application/vnd.openxmlformats-officedocument.wordprocessingml.template',
-      68 => 'application/vnd.rim.cod',
-      69 => 'application/vnd.smaf',
-      70 => 'application/vnd.stardivision.calc',
-      71 => 'application/vnd.stardivision.chart',
-      72 => 'application/vnd.stardivision.draw',
-      73 => 'application/vnd.stardivision.impress',
-      74 => 'application/vnd.stardivision.math',
-      75 => 'application/vnd.stardivision.writer',
-      76 => 'application/vnd.stardivision.writer-global',
-      77 => 'application/vnd.sun.xml.calc',
-      78 => 'application/vnd.sun.xml.calc.template',
-      79 => 'application/vnd.sun.xml.draw',
-      80 => 'application/vnd.sun.xml.draw.template',
-      81 => 'application/vnd.sun.xml.impress',
-      82 => 'application/vnd.sun.xml.impress.template',
-      83 => 'application/vnd.sun.xml.math',
-      84 => 'application/vnd.sun.xml.writer',
-      85 => 'application/vnd.sun.xml.writer.global',
-      86 => 'application/vnd.sun.xml.writer.template',
-      87 => 'application/vnd.symbian.install',
-      88 => 'application/vnd.visio',
-      89 => 'application/vnd.wap.wbxml',
-      90 => 'application/vnd.wap.wmlc',
-      91 => 'application/vnd.wap.wmlscriptc',
-      92 => 'application/wordperfect',
-      93 => 'application/wordperfect5.1',
-      94 => 'application/x-123',
-      95 => 'application/x-7z-compressed',
-      96 => 'application/x-abiword',
-      97 => 'application/x-apple-diskimage',
-      98 => 'application/x-bcpio',
-      99 => 'application/x-bittorrent',
-      100 => 'application/x-cab',
-      101 => 'application/x-cbr',
-      102 => 'application/x-cbz',
-      103 => 'application/x-cdf',
-      104 => 'application/x-cdlink',
-      105 => 'application/x-chess-pgn',
-      106 => 'application/x-cpio',
-      107 => 'application/x-debian-package',
-      108 => 'application/x-director',
-      109 => 'application/x-dms',
-      110 => 'application/x-doom',
-      111 => 'application/x-dvi',
-      112 => 'application/x-flac',
-      113 => 'application/x-font',
-      114 => 'application/x-freemind',
-      115 => 'application/x-futuresplash',
-      116 => 'application/x-gnumeric',
-      117 => 'application/x-go-sgf',
-      118 => 'application/x-graphing-calculator',
-      119 => 'application/x-gtar',
-      120 => 'application/x-hdf',
-      121 => 'application/x-httpd-eruby',
-      122 => 'application/x-httpd-php',
-      123 => 'application/x-httpd-php-source',
-      124 => 'application/x-httpd-php3',
-      125 => 'application/x-httpd-php3-preprocessed',
-      126 => 'application/x-httpd-php4',
-      127 => 'application/x-ica',
-      128 => 'application/x-internet-signup',
-      129 => 'application/x-iphone',
-      130 => 'application/x-iso9660-image',
-      131 => 'application/x-java-jnlp-file',
-      132 => 'application/x-javascript',
-      133 => 'application/x-jmol',
-      134 => 'application/x-kchart',
-      135 => 'application/x-killustrator',
-      136 => 'application/x-koan',
-      137 => 'application/x-kpresenter',
-      138 => 'application/x-kspread',
-      139 => 'application/x-kword',
-      140 => 'application/x-latex',
-      141 => 'application/x-lha',
-      142 => 'application/x-lyx',
-      143 => 'application/x-lzh',
-      144 => 'application/x-lzx',
-      145 => 'application/x-maker',
-      146 => 'application/x-mif',
-      351 => 'application/x-mobipocket-ebook',
-      352 => 'application/x-mobipocket-ebook',
-      147 => 'application/x-ms-wmd',
-      148 => 'application/x-ms-wmz',
-      149 => 'application/x-msdos-program',
-      150 => 'application/x-msi',
-      151 => 'application/x-netcdf',
-      152 => 'application/x-ns-proxy-autoconfig',
-      153 => 'application/x-nwc',
-      154 => 'application/x-object',
-      155 => 'application/x-oz-application',
-      156 => 'application/x-pkcs7-certreqresp',
-      157 => 'application/x-pkcs7-crl',
-      158 => 'application/x-python-code',
-      159 => 'application/x-quicktimeplayer',
-      160 => 'application/x-redhat-package-manager',
-      161 => 'application/x-shar',
-      162 => 'application/x-shockwave-flash',
-      163 => 'application/x-stuffit',
-      164 => 'application/x-sv4cpio',
-      165 => 'application/x-sv4crc',
-      166 => 'application/x-tar',
-      167 => 'application/x-tcl',
-      168 => 'application/x-tex-gf',
-      169 => 'application/x-tex-pk',
-      170 => 'application/x-texinfo',
-      171 => 'application/x-trash',
-      172 => 'application/x-troff',
-      173 => 'application/x-troff-man',
-      174 => 'application/x-troff-me',
-      175 => 'application/x-troff-ms',
-      176 => 'application/x-ustar',
-      177 => 'application/x-wais-source',
-      178 => 'application/x-wingz',
-      179 => 'application/x-x509-ca-cert',
-      180 => 'application/x-xcf',
-      181 => 'application/x-xfig',
-      182 => 'application/x-xpinstall',
-      183 => 'application/xhtml+xml',
-      184 => 'application/xml',
-      185 => 'application/zip',
-      186 => 'audio/basic',
-      187 => 'audio/midi',
-      346 => 'audio/mp4',
-      188 => 'audio/mpeg',
-      189 => 'audio/ogg',
-      190 => 'audio/prs.sid',
-      356 => 'audio/webm',
-      191 => 'audio/x-aiff',
-      192 => 'audio/x-gsm',
-      354 => 'audio/x-matroska',
-      193 => 'audio/x-mpegurl',
-      194 => 'audio/x-ms-wax',
-      195 => 'audio/x-ms-wma',
-      196 => 'audio/x-pn-realaudio',
-      197 => 'audio/x-realaudio',
-      198 => 'audio/x-scpls',
-      199 => 'audio/x-sd2',
-      200 => 'audio/x-wav',
-      201 => 'chemical/x-alchemy',
-      202 => 'chemical/x-cache',
-      203 => 'chemical/x-cache-csf',
-      204 => 'chemical/x-cactvs-binary',
-      205 => 'chemical/x-cdx',
-      206 => 'chemical/x-cerius',
-      207 => 'chemical/x-chem3d',
-      208 => 'chemical/x-chemdraw',
-      209 => 'chemical/x-cif',
-      210 => 'chemical/x-cmdf',
-      211 => 'chemical/x-cml',
-      212 => 'chemical/x-compass',
-      213 => 'chemical/x-crossfire',
-      214 => 'chemical/x-csml',
-      215 => 'chemical/x-ctx',
-      216 => 'chemical/x-cxf',
-      217 => 'chemical/x-embl-dl-nucleotide',
-      218 => 'chemical/x-galactic-spc',
-      219 => 'chemical/x-gamess-input',
-      220 => 'chemical/x-gaussian-checkpoint',
-      221 => 'chemical/x-gaussian-cube',
-      222 => 'chemical/x-gaussian-input',
-      223 => 'chemical/x-gaussian-log',
-      224 => 'chemical/x-gcg8-sequence',
-      225 => 'chemical/x-genbank',
-      226 => 'chemical/x-hin',
-      227 => 'chemical/x-isostar',
-      228 => 'chemical/x-jcamp-dx',
-      229 => 'chemical/x-kinemage',
-      230 => 'chemical/x-macmolecule',
-      231 => 'chemical/x-macromodel-input',
-      232 => 'chemical/x-mdl-molfile',
-      233 => 'chemical/x-mdl-rdfile',
-      234 => 'chemical/x-mdl-rxnfile',
-      235 => 'chemical/x-mdl-sdfile',
-      236 => 'chemical/x-mdl-tgf',
-      237 => 'chemical/x-mmcif',
-      238 => 'chemical/x-mol2',
-      239 => 'chemical/x-molconn-Z',
-      240 => 'chemical/x-mopac-graph',
-      241 => 'chemical/x-mopac-input',
-      242 => 'chemical/x-mopac-out',
-      243 => 'chemical/x-mopac-vib',
-      244 => 'chemical/x-ncbi-asn1-ascii',
-      245 => 'chemical/x-ncbi-asn1-binary',
-      246 => 'chemical/x-ncbi-asn1-spec',
-      247 => 'chemical/x-pdb',
-      248 => 'chemical/x-rosdal',
-      249 => 'chemical/x-swissprot',
-      250 => 'chemical/x-vamas-iso14976',
-      251 => 'chemical/x-vmd',
-      252 => 'chemical/x-xtel',
-      253 => 'chemical/x-xyz',
-      254 => 'image/gif',
-      255 => 'image/ief',
-      256 => 'image/jpeg',
-      257 => 'image/pcx',
-      258 => 'image/png',
-      259 => 'image/svg+xml',
-      260 => 'image/tiff',
-      261 => 'image/vnd.djvu',
-      262 => 'image/vnd.microsoft.icon',
-      263 => 'image/vnd.wap.wbmp',
-      355 => 'image/webp',
-      264 => 'image/x-cmu-raster',
-      265 => 'image/x-coreldraw',
-      266 => 'image/x-coreldrawpattern',
-      267 => 'image/x-coreldrawtemplate',
-      268 => 'image/x-corelphotopaint',
-      269 => 'image/x-jg',
-      270 => 'image/x-jng',
-      271 => 'image/x-ms-bmp',
-      272 => 'image/x-photoshop',
-      273 => 'image/x-portable-anymap',
-      274 => 'image/x-portable-bitmap',
-      275 => 'image/x-portable-graymap',
-      276 => 'image/x-portable-pixmap',
-      277 => 'image/x-rgb',
-      278 => 'image/x-xbitmap',
-      279 => 'image/x-xpixmap',
-      280 => 'image/x-xwindowdump',
-      281 => 'message/rfc822',
-      282 => 'model/iges',
-      283 => 'model/mesh',
-      284 => 'model/vrml',
-      285 => 'text/calendar',
-      286 => 'text/css',
-      287 => 'text/csv',
-      288 => 'text/h323',
-      289 => 'text/html',
-      290 => 'text/iuls',
-      291 => 'text/mathml',
-      292 => 'text/plain',
-      293 => 'text/richtext',
-      294 => 'text/scriptlet',
-      295 => 'text/tab-separated-values',
-      296 => 'text/texmacs',
-      297 => 'text/vnd.sun.j2me.app-descriptor',
-      298 => 'text/vnd.wap.wml',
-      299 => 'text/vnd.wap.wmlscript',
-      358 => 'text/vtt',
-      300 => 'text/x-bibtex',
-      301 => 'text/x-boo',
-      302 => 'text/x-c++hdr',
-      303 => 'text/x-c++src',
-      304 => 'text/x-chdr',
-      305 => 'text/x-component',
-      306 => 'text/x-csh',
-      307 => 'text/x-csrc',
-      308 => 'text/x-diff',
-      309 => 'text/x-dsrc',
-      310 => 'text/x-haskell',
-      311 => 'text/x-java',
-      312 => 'text/x-literate-haskell',
-      313 => 'text/x-moc',
-      314 => 'text/x-pascal',
-      315 => 'text/x-pcs-gcd',
-      316 => 'text/x-perl',
-      317 => 'text/x-python',
-      318 => 'text/x-setext',
-      319 => 'text/x-sh',
-      320 => 'text/x-tcl',
-      321 => 'text/x-tex',
-      322 => 'text/x-vcalendar',
-      323 => 'text/x-vcard',
-      324 => 'video/3gpp',
-      325 => 'video/dl',
-      326 => 'video/dv',
-      327 => 'video/fli',
-      328 => 'video/gl',
-      329 => 'video/mp4',
-      330 => 'video/mpeg',
-      331 => 'video/ogg',
-      332 => 'video/quicktime',
-      333 => 'video/vnd.mpegurl',
-      357 => 'video/webm',
-      347 => 'video/x-flv',
-      334 => 'video/x-la-asf',
-      348 => 'video/x-m4v',
-      353 => 'video/x-matroska',
-      335 => 'video/x-mng',
-      336 => 'video/x-ms-asf',
-      337 => 'video/x-ms-wm',
-      338 => 'video/x-ms-wmv',
-      339 => 'video/x-ms-wmx',
-      340 => 'video/x-ms-wvx',
-      341 => 'video/x-msvideo',
-      342 => 'video/x-sgi-movie',
-      343 => 'x-conference/x-cooltalk',
-      344 => 'x-epoc/x-sisx-app',
-      345 => 'x-world/x-vrml',
-    ),
+  protected $mapper;
 
-    // Extensions added to this list MUST be lower-case.
-    'extensions' => array(
-      'ez' => 0,
-      'atom' => 1,
-      'atomcat' => 2,
-      'atomsrv' => 3,
-      'cap' => 4,
-      'pcap' => 4,
-      'cu' => 5,
-      'tsp' => 6,
-      'hta' => 7,
-      'jar' => 8,
-      'ser' => 9,
-      'class' => 10,
-      'hqx' => 11,
-      'nb' => 12,
-      'mdb' => 13,
-      'dot' => 14,
-      'doc' => 14,
-      'bin' => 15,
-      'oda' => 16,
-      'ogx' => 17,
-      'pdf' => 18,
-      'key' => 19,
-      'pgp' => 20,
-      'prf' => 21,
-      'eps' => 22,
-      'ai' => 22,
-      'ps' => 22,
-      'rar' => 23,
-      'rdf' => 24,
-      'rss' => 25,
-      'rtf' => 26,
-      'smi' => 27,
-      'smil' => 27,
-      'cdy' => 28,
-      'kml' => 29,
-      'kmz' => 30,
-      'xul' => 31,
-      'xlb' => 32,
-      'xlt' => 32,
-      'xls' => 32,
-      'xlam' => 33,
-      'xlsb' => 34,
-      'xlsm' => 35,
-      'xltm' => 36,
-      'cat' => 37,
-      'stl' => 38,
-      'pps' => 39,
-      'ppt' => 39,
-      'ppam' => 40,
-      'pptm' => 41,
-      'ppsm' => 42,
-      'potm' => 43,
-      'docm' => 44,
-      'dotm' => 45,
-      'xps' => 46,
-      'odc' => 47,
-      'odb' => 48,
-      'odf' => 49,
-      'odg' => 50,
-      'otg' => 51,
-      'odi' => 52,
-      'odp' => 53,
-      'otp' => 54,
-      'ods' => 55,
-      'ots' => 56,
-      'odt' => 57,
-      'odm' => 58,
-      'ott' => 59,
-      'oth' => 60,
-      'pptx' => 61,
-      'ppsx' => 62,
-      'potx' => 63,
-      'xlsx' => 64,
-      'xltx' => 65,
-      'docx' => 66,
-      'dotx' => 67,
-      'cod' => 68,
-      'mmf' => 69,
-      'sdc' => 70,
-      'sds' => 71,
-      'sda' => 72,
-      'sdd' => 73,
-      'sdw' => 75,
-      'sgl' => 76,
-      'sxc' => 77,
-      'stc' => 78,
-      'sxd' => 79,
-      'std' => 80,
-      'sxi' => 81,
-      'sti' => 82,
-      'sxm' => 83,
-      'sxw' => 84,
-      'sxg' => 85,
-      'stw' => 86,
-      'sis' => 87,
-      'vsd' => 88,
-      'wbxml' => 89,
-      'wmlc' => 90,
-      'wmlsc' => 91,
-      'wpd' => 92,
-      'wp5' => 93,
-      'wk' => 94,
-      '7z' => 95,
-      'abw' => 96,
-      'dmg' => 97,
-      'bcpio' => 98,
-      'torrent' => 99,
-      'cab' => 100,
-      'cbr' => 101,
-      'cbz' => 102,
-      'cdf' => 103,
-      'vcd' => 104,
-      'pgn' => 105,
-      'cpio' => 106,
-      'udeb' => 107,
-      'deb' => 107,
-      'dir' => 108,
-      'dxr' => 108,
-      'dcr' => 108,
-      'dms' => 109,
-      'wad' => 110,
-      'dvi' => 111,
-      'flac' => 112,
-      'pfa' => 113,
-      'pfb' => 113,
-      'pcf' => 113,
-      'gsf' => 113,
-      'pcf.z' => 113,
-      'mm' => 114,
-      'spl' => 115,
-      'gnumeric' => 116,
-      'sgf' => 117,
-      'gcf' => 118,
-      'taz' => 119,
-      'gtar' => 119,
-      'tgz' => 119,
-      'hdf' => 120,
-      'rhtml' => 121,
-      'phtml' => 122,
-      'pht' => 122,
-      'php' => 122,
-      'phps' => 123,
-      'php3' => 124,
-      'php3p' => 125,
-      'php4' => 126,
-      'ica' => 127,
-      'ins' => 128,
-      'isp' => 128,
-      'iii' => 129,
-      'iso' => 130,
-      'jnlp' => 131,
-      'js' => 132,
-      'jmz' => 133,
-      'chrt' => 134,
-      'kil' => 135,
-      'skp' => 136,
-      'skd' => 136,
-      'skm' => 136,
-      'skt' => 136,
-      'kpr' => 137,
-      'kpt' => 137,
-      'ksp' => 138,
-      'kwd' => 139,
-      'kwt' => 139,
-      'latex' => 140,
-      'lha' => 141,
-      'lyx' => 142,
-      'lzh' => 143,
-      'lzx' => 144,
-      'maker' => 145,
-      'frm' => 145,
-      'frame' => 145,
-      'fm' => 145,
-      'book' => 145,
-      'fb' => 145,
-      'fbdoc' => 145,
-      'mif' => 146,
-      'wmd' => 147,
-      'wmz' => 148,
-      'dll' => 149,
-      'bat' => 149,
-      'exe' => 149,
-      'com' => 149,
-      'msi' => 150,
-      'nc' => 151,
-      'pac' => 152,
-      'nwc' => 153,
-      'o' => 154,
-      'oza' => 155,
-      'p7r' => 156,
-      'crl' => 157,
-      'pyo' => 158,
-      'pyc' => 158,
-      'qtl' => 159,
-      'rpm' => 160,
-      'shar' => 161,
-      'swf' => 162,
-      'swfl' => 162,
-      'sitx' => 163,
-      'sit' => 163,
-      'sv4cpio' => 164,
-      'sv4crc' => 165,
-      'tar' => 166,
-      'gf' => 168,
-      'pk' => 169,
-      'texi' => 170,
-      'texinfo' => 170,
-      'sik' => 171,
-      '~' => 171,
-      'bak' => 171,
-      '%' => 171,
-      'old' => 171,
-      't' => 172,
-      'roff' => 172,
-      'tr' => 172,
-      'man' => 173,
-      'me' => 174,
-      'ms' => 175,
-      'ustar' => 176,
-      'src' => 177,
-      'wz' => 178,
-      'crt' => 179,
-      'xcf' => 180,
-      'fig' => 181,
-      'xpi' => 182,
-      'xht' => 183,
-      'xhtml' => 183,
-      'xml' => 184,
-      'xsl' => 184,
-      'zip' => 185,
-      'au' => 186,
-      'snd' => 186,
-      'mid' => 187,
-      'midi' => 187,
-      'kar' => 187,
-      'mpega' => 188,
-      'mpga' => 188,
-      'm4a' => 188,
-      'mp3' => 188,
-      'mp2' => 188,
-      'ogg' => 189,
-      'oga' => 189,
-      'spx' => 189,
-      'sid' => 190,
-      'aif' => 191,
-      'aiff' => 191,
-      'aifc' => 191,
-      'gsm' => 192,
-      'm3u' => 193,
-      'wax' => 194,
-      'wma' => 195,
-      'rm' => 196,
-      'ram' => 196,
-      'ra' => 197,
-      'pls' => 198,
-      'sd2' => 199,
-      'wav' => 200,
-      'alc' => 201,
-      'cac' => 202,
-      'cache' => 202,
-      'csf' => 203,
-      'cascii' => 204,
-      'cbin' => 204,
-      'ctab' => 204,
-      'cdx' => 205,
-      'cer' => 206,
-      'c3d' => 207,
-      'chm' => 208,
-      'cif' => 209,
-      'cmdf' => 210,
-      'cml' => 211,
-      'cpa' => 212,
-      'bsd' => 213,
-      'csml' => 214,
-      'csm' => 214,
-      'ctx' => 215,
-      'cxf' => 216,
-      'cef' => 216,
-      'emb' => 217,
-      'embl' => 217,
-      'spc' => 218,
-      'gam' => 219,
-      'inp' => 219,
-      'gamin' => 219,
-      'fchk' => 220,
-      'fch' => 220,
-      'cub' => 221,
-      'gau' => 222,
-      'gjf' => 222,
-      'gjc' => 222,
-      'gal' => 223,
-      'gcg' => 224,
-      'gen' => 225,
-      'hin' => 226,
-      'istr' => 227,
-      'ist' => 227,
-      'dx' => 228,
-      'jdx' => 228,
-      'kin' => 229,
-      'mcm' => 230,
-      'mmd' => 231,
-      'mmod' => 231,
-      'mol' => 232,
-      'rd' => 233,
-      'rxn' => 234,
-      'sdf' => 235,
-      'sd' => 235,
-      'tgf' => 236,
-      'mcif' => 237,
-      'mol2' => 238,
-      'b' => 239,
-      'gpt' => 240,
-      'mopcrt' => 241,
-      'zmt' => 241,
-      'mpc' => 241,
-      'dat' => 241,
-      'mop' => 241,
-      'moo' => 242,
-      'mvb' => 243,
-      'prt' => 244,
-      'aso' => 245,
-      'val' => 245,
-      'asn' => 246,
-      'ent' => 247,
-      'pdb' => 247,
-      'ros' => 248,
-      'sw' => 249,
-      'vms' => 250,
-      'vmd' => 251,
-      'xtel' => 252,
-      'xyz' => 253,
-      'gif' => 254,
-      'ief' => 255,
-      'jpeg' => 256,
-      'jpe' => 256,
-      'jpg' => 256,
-      'pcx' => 257,
-      'png' => 258,
-      'svgz' => 259,
-      'svg' => 259,
-      'tif' => 260,
-      'tiff' => 260,
-      'djvu' => 261,
-      'djv' => 261,
-      'ico' => 262,
-      'wbmp' => 263,
-      'ras' => 264,
-      'cdr' => 265,
-      'pat' => 266,
-      'cdt' => 267,
-      'cpt' => 268,
-      'art' => 269,
-      'jng' => 270,
-      'bmp' => 271,
-      'psd' => 272,
-      'pnm' => 273,
-      'pbm' => 274,
-      'pgm' => 275,
-      'ppm' => 276,
-      'rgb' => 277,
-      'xbm' => 278,
-      'xpm' => 279,
-      'xwd' => 280,
-      'eml' => 281,
-      'igs' => 282,
-      'iges' => 282,
-      'silo' => 283,
-      'msh' => 283,
-      'mesh' => 283,
-      'icz' => 285,
-      'ics' => 285,
-      'css' => 286,
-      'csv' => 287,
-      '323' => 288,
-      'html' => 289,
-      'htm' => 289,
-      'shtml' => 289,
-      'uls' => 290,
-      'mml' => 291,
-      'txt' => 292,
-      'pot' => 292,
-      'text' => 292,
-      'asc' => 292,
-      'rtx' => 293,
-      'wsc' => 294,
-      'sct' => 294,
-      'tsv' => 295,
-      'ts' => 296,
-      'tm' => 296,
-      'jad' => 297,
-      'wml' => 298,
-      'wmls' => 299,
-      'bib' => 300,
-      'boo' => 301,
-      'hpp' => 302,
-      'hh' => 302,
-      'h++' => 302,
-      'hxx' => 302,
-      'cxx' => 303,
-      'cc' => 303,
-      'cpp' => 303,
-      'c++' => 303,
-      'h' => 304,
-      'htc' => 305,
-      'csh' => 306,
-      'c' => 307,
-      'patch' => 308,
-      'diff' => 308,
-      'd' => 309,
-      'hs' => 310,
-      'java' => 311,
-      'lhs' => 312,
-      'moc' => 313,
-      'pas' => 314,
-      'p' => 314,
-      'gcd' => 315,
-      'pm' => 316,
-      'pl' => 316,
-      'py' => 317,
-      'etx' => 318,
-      'sh' => 319,
-      'tk' => 320,
-      'tcl' => 320,
-      'cls' => 321,
-      'ltx' => 321,
-      'sty' => 321,
-      'tex' => 321,
-      'vcs' => 322,
-      'vcf' => 323,
-      '3gp' => 324,
-      'dl' => 325,
-      'dif' => 326,
-      'dv' => 326,
-      'fli' => 327,
-      'gl' => 328,
-      'mp4' => 329,
-      'f4v' => 329,
-      'f4p' => 329,
-      'mpe' => 330,
-      'mpeg' => 330,
-      'mpg' => 330,
-      'ogv' => 331,
-      'qt' => 332,
-      'mov' => 332,
-      'mxu' => 333,
-      'lsf' => 334,
-      'lsx' => 334,
-      'mng' => 335,
-      'asx' => 336,
-      'asf' => 336,
-      'wm' => 337,
-      'wmv' => 338,
-      'wmx' => 339,
-      'wvx' => 340,
-      'avi' => 341,
-      'movie' => 342,
-      'ice' => 343,
-      'sisx' => 344,
-      'wrl' => 345,
-      'vrm' => 345,
-      'vrml' => 345,
-      'f4a' => 346,
-      'f4b' => 346,
-      'flv' => 347,
-      'm4v' => 348,
-      'azw' => 349,
-      'epub' => 350,
-      'mobi' => 351,
-      'prc' => 352,
-      'mkv' => 353,
-      'mka' => 354,
-      'webp' => 355,
-      'weba' => 356,
-      'webm' => 357,
-      'vtt' => 358,
-    ),
-  );
+  /**
+   * Constructs a new ExtensionMimeTypeGuesser.
+   *
+   * @param MimeTypeMapperInterface $mapper
+   *   A MIME type mapper.
+   */
+  public function __construct(MimeTypeMapperInterface $mapper) {
+    $this->mapper = $mapper;
+  }
 
   /**
    * {@inheritdoc}
    */
   public function guess($path) {
+    $mapping = $this->mapper->getMapping();
     $extension = '';
     $file_parts = explode('.', drupal_basename($path));
 
@@ -881,12 +49,11 @@ public function guess($path) {
     //   - awesome.image.jpeg
     while ($additional_part = array_pop($file_parts)) {
       $extension = strtolower($additional_part . ($extension ? '.' . $extension : ''));
-      if (isset($this->mapping['extensions'][$extension])) {
-        return $this->mapping['mimetypes'][$this->mapping['extensions'][$extension]];
+      if (isset($mapping['extensions'][$extension])) {
+        return $mapping['mimetypes'][$mapping['extensions'][$extension]];
       }
     }
 
     return 'application/octet-stream';
   }
-
 }
diff --git a/core/lib/Drupal/Core/File/MimeType/MimeTypeMapper.php b/core/lib/Drupal/Core/File/MimeType/MimeTypeMapper.php
new file mode 100644
index 0000000..1f0299d
--- /dev/null
+++ b/core/lib/Drupal/Core/File/MimeType/MimeTypeMapper.php
@@ -0,0 +1,888 @@
+<?php
+/**
+ * @file
+ * Contains \Drupal\Core\File\MimeType\MimeTypeMapper.
+ */
+
+namespace Drupal\Core\File\MimeType;
+
+use Drupal\Core\Extension\ModuleHandlerInterface;
+
+/**
+ * Provides a sensible mapping between filename extensions and MIME types.
+ */
+class MimeTypeMapper implements MimeTypeMapperInterface {
+
+  /**
+   * Default MIME extension mapping.
+   *
+   * @var array
+   *   Array of mimetypes correlated to the extensions that relate to them.
+   */
+  protected $mapping = array(
+    'mimetypes' => array(
+      0 => 'application/andrew-inset',
+      1 => 'application/atom',
+      2 => 'application/atomcat+xml',
+      3 => 'application/atomserv+xml',
+      4 => 'application/cap',
+      5 => 'application/cu-seeme',
+      6 => 'application/dsptype',
+      350 => 'application/epub+zip',
+      7 => 'application/hta',
+      8 => 'application/java-archive',
+      9 => 'application/java-serialized-object',
+      10 => 'application/java-vm',
+      11 => 'application/mac-binhex40',
+      12 => 'application/mathematica',
+      13 => 'application/msaccess',
+      14 => 'application/msword',
+      15 => 'application/octet-stream',
+      16 => 'application/oda',
+      17 => 'application/ogg',
+      18 => 'application/pdf',
+      19 => 'application/pgp-keys',
+      20 => 'application/pgp-signature',
+      21 => 'application/pics-rules',
+      22 => 'application/postscript',
+      23 => 'application/rar',
+      24 => 'application/rdf+xml',
+      25 => 'application/rss+xml',
+      26 => 'application/rtf',
+      27 => 'application/smil',
+      349 => 'application/vnd.amazon.ebook',
+      28 => 'application/vnd.cinderella',
+      29 => 'application/vnd.google-earth.kml+xml',
+      30 => 'application/vnd.google-earth.kmz',
+      31 => 'application/vnd.mozilla.xul+xml',
+      32 => 'application/vnd.ms-excel',
+      33 => 'application/vnd.ms-excel.addin.macroEnabled.12',
+      34 => 'application/vnd.ms-excel.sheet.binary.macroEnabled.12',
+      35 => 'application/vnd.ms-excel.sheet.macroEnabled.12',
+      36 => 'application/vnd.ms-excel.template.macroEnabled.12',
+      37 => 'application/vnd.ms-pki.seccat',
+      38 => 'application/vnd.ms-pki.stl',
+      39 => 'application/vnd.ms-powerpoint',
+      40 => 'application/vnd.ms-powerpoint.addin.macroEnabled.12',
+      41 => 'application/vnd.ms-powerpoint.presentation.macroEnabled.12',
+      42 => 'application/vnd.ms-powerpoint.slideshow.macroEnabled.12',
+      43 => 'application/vnd.ms-powerpoint.template.macroEnabled.12',
+      44 => 'application/vnd.ms-word.document.macroEnabled.12',
+      45 => 'application/vnd.ms-word.template.macroEnabled.12',
+      46 => 'application/vnd.ms-xpsdocument',
+      47 => 'application/vnd.oasis.opendocument.chart',
+      48 => 'application/vnd.oasis.opendocument.database',
+      49 => 'application/vnd.oasis.opendocument.formula',
+      50 => 'application/vnd.oasis.opendocument.graphics',
+      51 => 'application/vnd.oasis.opendocument.graphics-template',
+      52 => 'application/vnd.oasis.opendocument.image',
+      53 => 'application/vnd.oasis.opendocument.presentation',
+      54 => 'application/vnd.oasis.opendocument.presentation-template',
+      55 => 'application/vnd.oasis.opendocument.spreadsheet',
+      56 => 'application/vnd.oasis.opendocument.spreadsheet-template',
+      57 => 'application/vnd.oasis.opendocument.text',
+      58 => 'application/vnd.oasis.opendocument.text-master',
+      59 => 'application/vnd.oasis.opendocument.text-template',
+      60 => 'application/vnd.oasis.opendocument.text-web',
+      61 => 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
+      62 => 'application/vnd.openxmlformats-officedocument.presentationml.slideshow',
+      63 => 'application/vnd.openxmlformats-officedocument.presentationml.template',
+      64 => 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
+      65 => 'application/vnd.openxmlformats-officedocument.spreadsheetml.template',
+      66 => 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
+      67 => 'application/vnd.openxmlformats-officedocument.wordprocessingml.template',
+      68 => 'application/vnd.rim.cod',
+      69 => 'application/vnd.smaf',
+      70 => 'application/vnd.stardivision.calc',
+      71 => 'application/vnd.stardivision.chart',
+      72 => 'application/vnd.stardivision.draw',
+      73 => 'application/vnd.stardivision.impress',
+      74 => 'application/vnd.stardivision.math',
+      75 => 'application/vnd.stardivision.writer',
+      76 => 'application/vnd.stardivision.writer-global',
+      77 => 'application/vnd.sun.xml.calc',
+      78 => 'application/vnd.sun.xml.calc.template',
+      79 => 'application/vnd.sun.xml.draw',
+      80 => 'application/vnd.sun.xml.draw.template',
+      81 => 'application/vnd.sun.xml.impress',
+      82 => 'application/vnd.sun.xml.impress.template',
+      83 => 'application/vnd.sun.xml.math',
+      84 => 'application/vnd.sun.xml.writer',
+      85 => 'application/vnd.sun.xml.writer.global',
+      86 => 'application/vnd.sun.xml.writer.template',
+      87 => 'application/vnd.symbian.install',
+      88 => 'application/vnd.visio',
+      89 => 'application/vnd.wap.wbxml',
+      90 => 'application/vnd.wap.wmlc',
+      91 => 'application/vnd.wap.wmlscriptc',
+      92 => 'application/wordperfect',
+      93 => 'application/wordperfect5.1',
+      94 => 'application/x-123',
+      95 => 'application/x-7z-compressed',
+      96 => 'application/x-abiword',
+      97 => 'application/x-apple-diskimage',
+      98 => 'application/x-bcpio',
+      99 => 'application/x-bittorrent',
+      100 => 'application/x-cab',
+      101 => 'application/x-cbr',
+      102 => 'application/x-cbz',
+      103 => 'application/x-cdf',
+      104 => 'application/x-cdlink',
+      105 => 'application/x-chess-pgn',
+      106 => 'application/x-cpio',
+      107 => 'application/x-debian-package',
+      108 => 'application/x-director',
+      109 => 'application/x-dms',
+      110 => 'application/x-doom',
+      111 => 'application/x-dvi',
+      112 => 'application/x-flac',
+      113 => 'application/x-font',
+      114 => 'application/x-freemind',
+      115 => 'application/x-futuresplash',
+      116 => 'application/x-gnumeric',
+      117 => 'application/x-go-sgf',
+      118 => 'application/x-graphing-calculator',
+      119 => 'application/x-gtar',
+      120 => 'application/x-hdf',
+      121 => 'application/x-httpd-eruby',
+      122 => 'application/x-httpd-php',
+      123 => 'application/x-httpd-php-source',
+      124 => 'application/x-httpd-php3',
+      125 => 'application/x-httpd-php3-preprocessed',
+      126 => 'application/x-httpd-php4',
+      127 => 'application/x-ica',
+      128 => 'application/x-internet-signup',
+      129 => 'application/x-iphone',
+      130 => 'application/x-iso9660-image',
+      131 => 'application/x-java-jnlp-file',
+      132 => 'application/x-javascript',
+      133 => 'application/x-jmol',
+      134 => 'application/x-kchart',
+      135 => 'application/x-killustrator',
+      136 => 'application/x-koan',
+      137 => 'application/x-kpresenter',
+      138 => 'application/x-kspread',
+      139 => 'application/x-kword',
+      140 => 'application/x-latex',
+      141 => 'application/x-lha',
+      142 => 'application/x-lyx',
+      143 => 'application/x-lzh',
+      144 => 'application/x-lzx',
+      145 => 'application/x-maker',
+      146 => 'application/x-mif',
+      351 => 'application/x-mobipocket-ebook',
+      352 => 'application/x-mobipocket-ebook',
+      147 => 'application/x-ms-wmd',
+      148 => 'application/x-ms-wmz',
+      149 => 'application/x-msdos-program',
+      150 => 'application/x-msi',
+      151 => 'application/x-netcdf',
+      152 => 'application/x-ns-proxy-autoconfig',
+      153 => 'application/x-nwc',
+      154 => 'application/x-object',
+      155 => 'application/x-oz-application',
+      156 => 'application/x-pkcs7-certreqresp',
+      157 => 'application/x-pkcs7-crl',
+      158 => 'application/x-python-code',
+      159 => 'application/x-quicktimeplayer',
+      160 => 'application/x-redhat-package-manager',
+      161 => 'application/x-shar',
+      162 => 'application/x-shockwave-flash',
+      163 => 'application/x-stuffit',
+      164 => 'application/x-sv4cpio',
+      165 => 'application/x-sv4crc',
+      166 => 'application/x-tar',
+      167 => 'application/x-tcl',
+      168 => 'application/x-tex-gf',
+      169 => 'application/x-tex-pk',
+      170 => 'application/x-texinfo',
+      171 => 'application/x-trash',
+      172 => 'application/x-troff',
+      173 => 'application/x-troff-man',
+      174 => 'application/x-troff-me',
+      175 => 'application/x-troff-ms',
+      176 => 'application/x-ustar',
+      177 => 'application/x-wais-source',
+      178 => 'application/x-wingz',
+      179 => 'application/x-x509-ca-cert',
+      180 => 'application/x-xcf',
+      181 => 'application/x-xfig',
+      182 => 'application/x-xpinstall',
+      183 => 'application/xhtml+xml',
+      184 => 'application/xml',
+      185 => 'application/zip',
+      186 => 'audio/basic',
+      187 => 'audio/midi',
+      346 => 'audio/mp4',
+      188 => 'audio/mpeg',
+      189 => 'audio/ogg',
+      190 => 'audio/prs.sid',
+      356 => 'audio/webm',
+      191 => 'audio/x-aiff',
+      192 => 'audio/x-gsm',
+      354 => 'audio/x-matroska',
+      193 => 'audio/x-mpegurl',
+      194 => 'audio/x-ms-wax',
+      195 => 'audio/x-ms-wma',
+      196 => 'audio/x-pn-realaudio',
+      197 => 'audio/x-realaudio',
+      198 => 'audio/x-scpls',
+      199 => 'audio/x-sd2',
+      200 => 'audio/x-wav',
+      201 => 'chemical/x-alchemy',
+      202 => 'chemical/x-cache',
+      203 => 'chemical/x-cache-csf',
+      204 => 'chemical/x-cactvs-binary',
+      205 => 'chemical/x-cdx',
+      206 => 'chemical/x-cerius',
+      207 => 'chemical/x-chem3d',
+      208 => 'chemical/x-chemdraw',
+      209 => 'chemical/x-cif',
+      210 => 'chemical/x-cmdf',
+      211 => 'chemical/x-cml',
+      212 => 'chemical/x-compass',
+      213 => 'chemical/x-crossfire',
+      214 => 'chemical/x-csml',
+      215 => 'chemical/x-ctx',
+      216 => 'chemical/x-cxf',
+      217 => 'chemical/x-embl-dl-nucleotide',
+      218 => 'chemical/x-galactic-spc',
+      219 => 'chemical/x-gamess-input',
+      220 => 'chemical/x-gaussian-checkpoint',
+      221 => 'chemical/x-gaussian-cube',
+      222 => 'chemical/x-gaussian-input',
+      223 => 'chemical/x-gaussian-log',
+      224 => 'chemical/x-gcg8-sequence',
+      225 => 'chemical/x-genbank',
+      226 => 'chemical/x-hin',
+      227 => 'chemical/x-isostar',
+      228 => 'chemical/x-jcamp-dx',
+      229 => 'chemical/x-kinemage',
+      230 => 'chemical/x-macmolecule',
+      231 => 'chemical/x-macromodel-input',
+      232 => 'chemical/x-mdl-molfile',
+      233 => 'chemical/x-mdl-rdfile',
+      234 => 'chemical/x-mdl-rxnfile',
+      235 => 'chemical/x-mdl-sdfile',
+      236 => 'chemical/x-mdl-tgf',
+      237 => 'chemical/x-mmcif',
+      238 => 'chemical/x-mol2',
+      239 => 'chemical/x-molconn-Z',
+      240 => 'chemical/x-mopac-graph',
+      241 => 'chemical/x-mopac-input',
+      242 => 'chemical/x-mopac-out',
+      243 => 'chemical/x-mopac-vib',
+      244 => 'chemical/x-ncbi-asn1-ascii',
+      245 => 'chemical/x-ncbi-asn1-binary',
+      246 => 'chemical/x-ncbi-asn1-spec',
+      247 => 'chemical/x-pdb',
+      248 => 'chemical/x-rosdal',
+      249 => 'chemical/x-swissprot',
+      250 => 'chemical/x-vamas-iso14976',
+      251 => 'chemical/x-vmd',
+      252 => 'chemical/x-xtel',
+      253 => 'chemical/x-xyz',
+      254 => 'image/gif',
+      255 => 'image/ief',
+      256 => 'image/jpeg',
+      257 => 'image/pcx',
+      258 => 'image/png',
+      259 => 'image/svg+xml',
+      260 => 'image/tiff',
+      261 => 'image/vnd.djvu',
+      262 => 'image/vnd.microsoft.icon',
+      263 => 'image/vnd.wap.wbmp',
+      355 => 'image/webp',
+      264 => 'image/x-cmu-raster',
+      265 => 'image/x-coreldraw',
+      266 => 'image/x-coreldrawpattern',
+      267 => 'image/x-coreldrawtemplate',
+      268 => 'image/x-corelphotopaint',
+      269 => 'image/x-jg',
+      270 => 'image/x-jng',
+      271 => 'image/x-ms-bmp',
+      272 => 'image/x-photoshop',
+      273 => 'image/x-portable-anymap',
+      274 => 'image/x-portable-bitmap',
+      275 => 'image/x-portable-graymap',
+      276 => 'image/x-portable-pixmap',
+      277 => 'image/x-rgb',
+      278 => 'image/x-xbitmap',
+      279 => 'image/x-xpixmap',
+      280 => 'image/x-xwindowdump',
+      281 => 'message/rfc822',
+      282 => 'model/iges',
+      283 => 'model/mesh',
+      284 => 'model/vrml',
+      285 => 'text/calendar',
+      286 => 'text/css',
+      287 => 'text/csv',
+      288 => 'text/h323',
+      289 => 'text/html',
+      290 => 'text/iuls',
+      291 => 'text/mathml',
+      292 => 'text/plain',
+      293 => 'text/richtext',
+      294 => 'text/scriptlet',
+      295 => 'text/tab-separated-values',
+      296 => 'text/texmacs',
+      297 => 'text/vnd.sun.j2me.app-descriptor',
+      298 => 'text/vnd.wap.wml',
+      299 => 'text/vnd.wap.wmlscript',
+      358 => 'text/vtt',
+      300 => 'text/x-bibtex',
+      301 => 'text/x-boo',
+      302 => 'text/x-c++hdr',
+      303 => 'text/x-c++src',
+      304 => 'text/x-chdr',
+      305 => 'text/x-component',
+      306 => 'text/x-csh',
+      307 => 'text/x-csrc',
+      308 => 'text/x-diff',
+      309 => 'text/x-dsrc',
+      310 => 'text/x-haskell',
+      311 => 'text/x-java',
+      312 => 'text/x-literate-haskell',
+      313 => 'text/x-moc',
+      314 => 'text/x-pascal',
+      315 => 'text/x-pcs-gcd',
+      316 => 'text/x-perl',
+      317 => 'text/x-python',
+      318 => 'text/x-setext',
+      319 => 'text/x-sh',
+      320 => 'text/x-tcl',
+      321 => 'text/x-tex',
+      322 => 'text/x-vcalendar',
+      323 => 'text/x-vcard',
+      324 => 'video/3gpp',
+      325 => 'video/dl',
+      326 => 'video/dv',
+      327 => 'video/fli',
+      328 => 'video/gl',
+      329 => 'video/mp4',
+      330 => 'video/mpeg',
+      331 => 'video/ogg',
+      332 => 'video/quicktime',
+      333 => 'video/vnd.mpegurl',
+      357 => 'video/webm',
+      347 => 'video/x-flv',
+      334 => 'video/x-la-asf',
+      348 => 'video/x-m4v',
+      353 => 'video/x-matroska',
+      335 => 'video/x-mng',
+      336 => 'video/x-ms-asf',
+      337 => 'video/x-ms-wm',
+      338 => 'video/x-ms-wmv',
+      339 => 'video/x-ms-wmx',
+      340 => 'video/x-ms-wvx',
+      341 => 'video/x-msvideo',
+      342 => 'video/x-sgi-movie',
+      343 => 'x-conference/x-cooltalk',
+      344 => 'x-epoc/x-sisx-app',
+      345 => 'x-world/x-vrml',
+    ),
+
+    // Extensions added to this list MUST be lower-case.
+    'extensions' => array(
+      'ez' => 0,
+      'atom' => 1,
+      'atomcat' => 2,
+      'atomsrv' => 3,
+      'cap' => 4,
+      'pcap' => 4,
+      'cu' => 5,
+      'tsp' => 6,
+      'hta' => 7,
+      'jar' => 8,
+      'ser' => 9,
+      'class' => 10,
+      'hqx' => 11,
+      'nb' => 12,
+      'mdb' => 13,
+      'dot' => 14,
+      'doc' => 14,
+      'bin' => 15,
+      'oda' => 16,
+      'ogx' => 17,
+      'pdf' => 18,
+      'key' => 19,
+      'pgp' => 20,
+      'prf' => 21,
+      'eps' => 22,
+      'ai' => 22,
+      'ps' => 22,
+      'rar' => 23,
+      'rdf' => 24,
+      'rss' => 25,
+      'rtf' => 26,
+      'smi' => 27,
+      'smil' => 27,
+      'cdy' => 28,
+      'kml' => 29,
+      'kmz' => 30,
+      'xul' => 31,
+      'xlb' => 32,
+      'xlt' => 32,
+      'xls' => 32,
+      'xlam' => 33,
+      'xlsb' => 34,
+      'xlsm' => 35,
+      'xltm' => 36,
+      'cat' => 37,
+      'stl' => 38,
+      'pps' => 39,
+      'ppt' => 39,
+      'ppam' => 40,
+      'pptm' => 41,
+      'ppsm' => 42,
+      'potm' => 43,
+      'docm' => 44,
+      'dotm' => 45,
+      'xps' => 46,
+      'odc' => 47,
+      'odb' => 48,
+      'odf' => 49,
+      'odg' => 50,
+      'otg' => 51,
+      'odi' => 52,
+      'odp' => 53,
+      'otp' => 54,
+      'ods' => 55,
+      'ots' => 56,
+      'odt' => 57,
+      'odm' => 58,
+      'ott' => 59,
+      'oth' => 60,
+      'pptx' => 61,
+      'ppsx' => 62,
+      'potx' => 63,
+      'xlsx' => 64,
+      'xltx' => 65,
+      'docx' => 66,
+      'dotx' => 67,
+      'cod' => 68,
+      'mmf' => 69,
+      'sdc' => 70,
+      'sds' => 71,
+      'sda' => 72,
+      'sdd' => 73,
+      'sdw' => 75,
+      'sgl' => 76,
+      'sxc' => 77,
+      'stc' => 78,
+      'sxd' => 79,
+      'std' => 80,
+      'sxi' => 81,
+      'sti' => 82,
+      'sxm' => 83,
+      'sxw' => 84,
+      'sxg' => 85,
+      'stw' => 86,
+      'sis' => 87,
+      'vsd' => 88,
+      'wbxml' => 89,
+      'wmlc' => 90,
+      'wmlsc' => 91,
+      'wpd' => 92,
+      'wp5' => 93,
+      'wk' => 94,
+      '7z' => 95,
+      'abw' => 96,
+      'dmg' => 97,
+      'bcpio' => 98,
+      'torrent' => 99,
+      'cab' => 100,
+      'cbr' => 101,
+      'cbz' => 102,
+      'cdf' => 103,
+      'vcd' => 104,
+      'pgn' => 105,
+      'cpio' => 106,
+      'udeb' => 107,
+      'deb' => 107,
+      'dir' => 108,
+      'dxr' => 108,
+      'dcr' => 108,
+      'dms' => 109,
+      'wad' => 110,
+      'dvi' => 111,
+      'flac' => 112,
+      'pfa' => 113,
+      'pfb' => 113,
+      'pcf' => 113,
+      'gsf' => 113,
+      'pcf.z' => 113,
+      'mm' => 114,
+      'spl' => 115,
+      'gnumeric' => 116,
+      'sgf' => 117,
+      'gcf' => 118,
+      'taz' => 119,
+      'gtar' => 119,
+      'tgz' => 119,
+      'hdf' => 120,
+      'rhtml' => 121,
+      'phtml' => 122,
+      'pht' => 122,
+      'php' => 122,
+      'phps' => 123,
+      'php3' => 124,
+      'php3p' => 125,
+      'php4' => 126,
+      'ica' => 127,
+      'ins' => 128,
+      'isp' => 128,
+      'iii' => 129,
+      'iso' => 130,
+      'jnlp' => 131,
+      'js' => 132,
+      'jmz' => 133,
+      'chrt' => 134,
+      'kil' => 135,
+      'skp' => 136,
+      'skd' => 136,
+      'skm' => 136,
+      'skt' => 136,
+      'kpr' => 137,
+      'kpt' => 137,
+      'ksp' => 138,
+      'kwd' => 139,
+      'kwt' => 139,
+      'latex' => 140,
+      'lha' => 141,
+      'lyx' => 142,
+      'lzh' => 143,
+      'lzx' => 144,
+      'maker' => 145,
+      'frm' => 145,
+      'frame' => 145,
+      'fm' => 145,
+      'book' => 145,
+      'fb' => 145,
+      'fbdoc' => 145,
+      'mif' => 146,
+      'wmd' => 147,
+      'wmz' => 148,
+      'dll' => 149,
+      'bat' => 149,
+      'exe' => 149,
+      'com' => 149,
+      'msi' => 150,
+      'nc' => 151,
+      'pac' => 152,
+      'nwc' => 153,
+      'o' => 154,
+      'oza' => 155,
+      'p7r' => 156,
+      'crl' => 157,
+      'pyo' => 158,
+      'pyc' => 158,
+      'qtl' => 159,
+      'rpm' => 160,
+      'shar' => 161,
+      'swf' => 162,
+      'swfl' => 162,
+      'sitx' => 163,
+      'sit' => 163,
+      'sv4cpio' => 164,
+      'sv4crc' => 165,
+      'tar' => 166,
+      'gf' => 168,
+      'pk' => 169,
+      'texi' => 170,
+      'texinfo' => 170,
+      'sik' => 171,
+      '~' => 171,
+      'bak' => 171,
+      '%' => 171,
+      'old' => 171,
+      't' => 172,
+      'roff' => 172,
+      'tr' => 172,
+      'man' => 173,
+      'me' => 174,
+      'ms' => 175,
+      'ustar' => 176,
+      'src' => 177,
+      'wz' => 178,
+      'crt' => 179,
+      'xcf' => 180,
+      'fig' => 181,
+      'xpi' => 182,
+      'xht' => 183,
+      'xhtml' => 183,
+      'xml' => 184,
+      'xsl' => 184,
+      'zip' => 185,
+      'au' => 186,
+      'snd' => 186,
+      'mid' => 187,
+      'midi' => 187,
+      'kar' => 187,
+      'mpega' => 188,
+      'mpga' => 188,
+      'm4a' => 188,
+      'mp3' => 188,
+      'mp2' => 188,
+      'ogg' => 189,
+      'oga' => 189,
+      'spx' => 189,
+      'sid' => 190,
+      'aif' => 191,
+      'aiff' => 191,
+      'aifc' => 191,
+      'gsm' => 192,
+      'm3u' => 193,
+      'wax' => 194,
+      'wma' => 195,
+      'rm' => 196,
+      'ram' => 196,
+      'ra' => 197,
+      'pls' => 198,
+      'sd2' => 199,
+      'wav' => 200,
+      'alc' => 201,
+      'cac' => 202,
+      'cache' => 202,
+      'csf' => 203,
+      'cascii' => 204,
+      'cbin' => 204,
+      'ctab' => 204,
+      'cdx' => 205,
+      'cer' => 206,
+      'c3d' => 207,
+      'chm' => 208,
+      'cif' => 209,
+      'cmdf' => 210,
+      'cml' => 211,
+      'cpa' => 212,
+      'bsd' => 213,
+      'csml' => 214,
+      'csm' => 214,
+      'ctx' => 215,
+      'cxf' => 216,
+      'cef' => 216,
+      'emb' => 217,
+      'embl' => 217,
+      'spc' => 218,
+      'gam' => 219,
+      'inp' => 219,
+      'gamin' => 219,
+      'fchk' => 220,
+      'fch' => 220,
+      'cub' => 221,
+      'gau' => 222,
+      'gjf' => 222,
+      'gjc' => 222,
+      'gal' => 223,
+      'gcg' => 224,
+      'gen' => 225,
+      'hin' => 226,
+      'istr' => 227,
+      'ist' => 227,
+      'dx' => 228,
+      'jdx' => 228,
+      'kin' => 229,
+      'mcm' => 230,
+      'mmd' => 231,
+      'mmod' => 231,
+      'mol' => 232,
+      'rd' => 233,
+      'rxn' => 234,
+      'sdf' => 235,
+      'sd' => 235,
+      'tgf' => 236,
+      'mcif' => 237,
+      'mol2' => 238,
+      'b' => 239,
+      'gpt' => 240,
+      'mopcrt' => 241,
+      'zmt' => 241,
+      'mpc' => 241,
+      'dat' => 241,
+      'mop' => 241,
+      'moo' => 242,
+      'mvb' => 243,
+      'prt' => 244,
+      'aso' => 245,
+      'val' => 245,
+      'asn' => 246,
+      'ent' => 247,
+      'pdb' => 247,
+      'ros' => 248,
+      'sw' => 249,
+      'vms' => 250,
+      'vmd' => 251,
+      'xtel' => 252,
+      'xyz' => 253,
+      'gif' => 254,
+      'ief' => 255,
+      'jpeg' => 256,
+      'jpe' => 256,
+      'jpg' => 256,
+      'pcx' => 257,
+      'png' => 258,
+      'svgz' => 259,
+      'svg' => 259,
+      'tif' => 260,
+      'tiff' => 260,
+      'djvu' => 261,
+      'djv' => 261,
+      'ico' => 262,
+      'wbmp' => 263,
+      'ras' => 264,
+      'cdr' => 265,
+      'pat' => 266,
+      'cdt' => 267,
+      'cpt' => 268,
+      'art' => 269,
+      'jng' => 270,
+      'bmp' => 271,
+      'psd' => 272,
+      'pnm' => 273,
+      'pbm' => 274,
+      'pgm' => 275,
+      'ppm' => 276,
+      'rgb' => 277,
+      'xbm' => 278,
+      'xpm' => 279,
+      'xwd' => 280,
+      'eml' => 281,
+      'igs' => 282,
+      'iges' => 282,
+      'silo' => 283,
+      'msh' => 283,
+      'mesh' => 283,
+      'icz' => 285,
+      'ics' => 285,
+      'css' => 286,
+      'csv' => 287,
+      '323' => 288,
+      'html' => 289,
+      'htm' => 289,
+      'shtml' => 289,
+      'uls' => 290,
+      'mml' => 291,
+      'txt' => 292,
+      'pot' => 292,
+      'text' => 292,
+      'asc' => 292,
+      'rtx' => 293,
+      'wsc' => 294,
+      'sct' => 294,
+      'tsv' => 295,
+      'ts' => 296,
+      'tm' => 296,
+      'jad' => 297,
+      'wml' => 298,
+      'wmls' => 299,
+      'bib' => 300,
+      'boo' => 301,
+      'hpp' => 302,
+      'hh' => 302,
+      'h++' => 302,
+      'hxx' => 302,
+      'cxx' => 303,
+      'cc' => 303,
+      'cpp' => 303,
+      'c++' => 303,
+      'h' => 304,
+      'htc' => 305,
+      'csh' => 306,
+      'c' => 307,
+      'patch' => 308,
+      'diff' => 308,
+      'd' => 309,
+      'hs' => 310,
+      'java' => 311,
+      'lhs' => 312,
+      'moc' => 313,
+      'pas' => 314,
+      'p' => 314,
+      'gcd' => 315,
+      'pm' => 316,
+      'pl' => 316,
+      'py' => 317,
+      'etx' => 318,
+      'sh' => 319,
+      'tk' => 320,
+      'tcl' => 320,
+      'cls' => 321,
+      'ltx' => 321,
+      'sty' => 321,
+      'tex' => 321,
+      'vcs' => 322,
+      'vcf' => 323,
+      '3gp' => 324,
+      'dl' => 325,
+      'dif' => 326,
+      'dv' => 326,
+      'fli' => 327,
+      'gl' => 328,
+      'mp4' => 329,
+      'f4v' => 329,
+      'f4p' => 329,
+      'mpe' => 330,
+      'mpeg' => 330,
+      'mpg' => 330,
+      'ogv' => 331,
+      'qt' => 332,
+      'mov' => 332,
+      'mxu' => 333,
+      'lsf' => 334,
+      'lsx' => 334,
+      'mng' => 335,
+      'asx' => 336,
+      'asf' => 336,
+      'wm' => 337,
+      'wmv' => 338,
+      'wmx' => 339,
+      'wvx' => 340,
+      'avi' => 341,
+      'movie' => 342,
+      'ice' => 343,
+      'sisx' => 344,
+      'wrl' => 345,
+      'vrm' => 345,
+      'vrml' => 345,
+      'f4a' => 346,
+      'f4b' => 346,
+      'flv' => 347,
+      'm4v' => 348,
+      'azw' => 349,
+      'epub' => 350,
+      'mobi' => 351,
+      'prc' => 352,
+      'mkv' => 353,
+      'mka' => 354,
+      'webp' => 355,
+      'weba' => 356,
+      'webm' => 357,
+      'vtt' => 358,
+    ),
+  );
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getMapping() {
+    return $this->mapping;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getMimeTypes() {
+    list($mimetypes,) = $this->getMapping();
+    return $mimetypes;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getMimeTypeForExtension($extension) {
+    list($mimetypes, $extensions) = $this->getMapping();
+    $extension = strtolower($extension);
+    return isset($extensions[$extension]) ? $mimetypes[$extensions[$extension]] : NULL;
+  }
+}
diff --git a/core/lib/Drupal/Core/File/MimeType/MimeTypeMapperInterface.php b/core/lib/Drupal/Core/File/MimeType/MimeTypeMapperInterface.php
new file mode 100644
index 0000000..c348193
--- /dev/null
+++ b/core/lib/Drupal/Core/File/MimeType/MimeTypeMapperInterface.php
@@ -0,0 +1,43 @@
+<?php
+/**
+ * @file
+ * Contains \Drupal\Core\File\MimeType\MimeTypeMapperInterface.
+ */
+
+namespace Drupal\Core\File\MimeType;
+
+/**
+ * Provides a sensible mapping between filename extensions and MIME types.
+ */
+interface MimeTypeMapperInterface {
+  /**
+   * Returns known MIME types.
+   *
+   * @return string[]
+   *   An indexed array of MIME types.
+   */
+  public function getMimeTypes();
+
+  /**
+   * Returns a mapping from file extensions to appropriate MIME types.
+   *
+   * @return array
+   *   An array consisting of two arrays:
+   *     - mimetypes: MIME types, keyed by a unique number.
+   *     - extensions: an associative array with the MIME type key numbers as
+   *       values. The keys are file extensions, in lower case and without any
+   *       preceding dot.
+   */
+  public function getMapping();
+
+  /**
+   * Returns the appropriate MIME type for a given file extension.
+   *
+   * @param string $extension
+   *   A file extension, without leading dot.
+   *
+   * @return string|null
+   *   A matching MIME type, or NULL if no MIME type matches the extension.
+   */
+  public function getMimeTypeForExtension($extension);
+}