Add support for popular e-book formats, Google web formats, mkv and mka in file_default_mimetype_mapping()

I'm going to leave this for someone who's new to core development :)

Added the above mimetypes.

Adding the other two extensions from very similar issue: http://drupal.org/node/1293140 - add support for mka and mkv.

Added support for the following extensions:
+ 'azw' => 349,
+ 'epub' => 350,
+ 'mobi' => 351,
+ 'prc' => 352,
+ 'mkv' => 353,
+ 'mka' => 354,
+ 'webp' => 355,
+ 'weba' => 356,
+ 'webm' => 357,
+ 'vtt' => 358,

#10 applies cleanly. Tested using 10 files with the extensions in question.

Here are a couple of screenshots showing the new mimetypes at work:

Any reason why these are being added with out of sequence array indices?

+++ b/core/includes/file.mimetypes.incundefined
@@ -64,6 +65,7 @@ function file_default_mimetype_mapping() {
       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',

Let's re-number the array instead of putting out of sequence array indices.

We should just re-index the array - i.e. have it both alphabetical, and the numeric keys in sequence. That will mean the index changes for some file types but that should be a problem since code shouldn't be dealing with the indexes directly anyway.

I don't see a reason not to fix that before this goes in, the fact that another patch already made it wonky doesn't feel like a reason to make it even worse.

I'm not entirely familiar with the usage here, but if the code should never deal with the indexes directly, then why do we have them? Could we just do away with them entirely?

Is it possible to have patch #10 applied to Drupal 8 and backported to 7 before this refactoring process is started? Or just to Drupal 7?

I think we could backport a re-numbering of the array to D7, assigning to David for comment.

Well, if my reading of hook_file_mimetype_mapping_alter() is correct, those numbers are actually meaningful (people are intended to refer to them directly in the alter hook, as in the example code used there)... If that's the case, we shouldn't renumber them in Drupal 7.

There is precedence for adding mimetypes out of order see #370958: FLV Flash Video Mimetypes. I don't think we should get to hung up on the order of the array - preserving the numbers for existing code seems more in our interests.

Committed fc4150b and pushed to 8.x. Thanks!

Uploading D7 backport containing the mimetypes from ExtensionMimeTypeGuesser.php in 8.x branch. List remains out of order. Screenshots attached of the new mimetypes working properly.

Looks good to me. RTBC.

Committed to 7.x - thanks!