diff -u b/core/modules/file/config/schema/file.schema.yml b/core/modules/file/config/schema/file.schema.yml
--- b/core/modules/file/config/schema/file.schema.yml
+++ b/core/modules/file/config/schema/file.schema.yml
@@ -76,7 +76,7 @@
   mapping:
     controls:
       type: boolean
-      label: 'Show audio controls'
+      label: 'Show controls'
     autoplay:
       type: boolean
       label: 'Autoplay'
diff -u b/core/modules/file/src/Plugin/Field/FieldFormatter/FileAudioFormatter.php b/core/modules/file/src/Plugin/Field/FieldFormatter/FileAudioFormatter.php
--- b/core/modules/file/src/Plugin/Field/FieldFormatter/FileAudioFormatter.php
+++ b/core/modules/file/src/Plugin/Field/FieldFormatter/FileAudioFormatter.php
@@ -20,5 +20,7 @@
    * {@inheritdoc}
    */
-  const APPLICABLE_MIME_TYPE = 'audio';
+  public static function getMimeType() {
+    return 'audio';
+  }
 
 }
diff -u b/core/modules/file/src/Plugin/Field/FieldFormatter/FileMediaFormatter.php b/core/modules/file/src/Plugin/Field/FieldFormatter/FileMediaFormatter.php
--- b/core/modules/file/src/Plugin/Field/FieldFormatter/FileMediaFormatter.php
+++ b/core/modules/file/src/Plugin/Field/FieldFormatter/FileMediaFormatter.php
@@ -10,17 +10,11 @@
 use Drupal\Core\Render\RendererInterface;
 use Drupal\Core\Template\Attribute;
 use Symfony\Component\DependencyInjection\ContainerInterface;
-use Symfony\Component\HttpFoundation\File\MimeType\MimeTypeGuesserInterface;
 
 /**
  * Base class for media file formatter.
  */
-abstract class FileMediaFormatter extends FileFormatterBase implements ContainerFactoryPluginInterface {
-
-  /**
-   * The applicable mimetype for a formatter.
-   */
-  const APPLICABLE_MIME_TYPE = FALSE;
+abstract class FileMediaFormatter extends FileFormatterBase implements ContainerFactoryPluginInterface, FileMediaFormatterInterface {
 
   /**
    * The renderer service.
@@ -75,41 +69,41 @@
    */
   public static function defaultSettings() {
     return [
-        'controls' => TRUE,
-        'autoplay' => FALSE,
-        'loop' => FALSE,
-        'multiple_file_behavior' => 'tags',
-      ] + parent::defaultSettings();
+      'controls' => TRUE,
+      'autoplay' => FALSE,
+      'loop' => FALSE,
+      'multiple_file_behavior' => 'tags',
+    ] + parent::defaultSettings();
   }
 
   /**
    * {@inheritdoc}
    */
   public function settingsForm(array $form, FormStateInterface $form_state) {
-    $element['controls'] = array(
+    $element['controls'] = [
       '#title' => $this->t('Show audio controls'),
       '#type' => 'checkbox',
       '#default_value' => $this->getSetting('controls'),
-    );
-    $element['autoplay'] = array(
+    ];
+    $element['autoplay'] = [
       '#title' => $this->t('Autoplay'),
       '#type' => 'checkbox',
       '#default_value' => $this->getSetting('autoplay'),
-    );
-    $element['loop'] = array(
+    ];
+    $element['loop'] = [
       '#title' => $this->t('Loop'),
       '#type' => 'checkbox',
       '#default_value' => $this->getSetting('loop'),
-    );
-    $element['multiple_file_behavior'] = array(
+    ];
+    $element['multiple_file_behavior'] = [
       '#title' => $this->t('Display of multiple files'),
       '#type' => 'radios',
-      '#options' => array(
-        'tags' => $this->t('Use multiple @tag tags, each with a single source.', array('@tag' => '<' . static::APPLICABLE_MIME_TYPE . '>')),
-        'sources' => $this->t('Use multiple sources within a single @tag tag.', array('@tag' => '<' . static::APPLICABLE_MIME_TYPE . '>')),
-      ),
+      '#options' => [
+        'tags' => $this->t('Use multiple @tag tags, each with a single source.', ['@tag' => '<' . static::getMimeType() . '>']),
+        'sources' => $this->t('Use multiple sources within a single @tag tag.', ['@tag' => '<' . static::getMimeType() . '>']),
+      ],
       '#default_value' => $this->getSetting('multiple_file_behavior'),
-    );
+    ];
 
     return $element;
   }
@@ -118,20 +112,18 @@
    * {@inheritdoc}
    */
   public static function isApplicable(FieldDefinitionInterface $field_definition) {
-
     if (!parent::isApplicable($field_definition)) {
       return FALSE;
     }
 
-    /** @var MimeTypeGuesserInterface $extension_mime_type_guesser */
+    /** @var \Symfony\Component\HttpFoundation\File\MimeType\MimeTypeGuesserInterface $extension_mime_type_guesser */
     $extension_mime_type_guesser = \Drupal::service('file.mime_type.guesser.extension');
+    $extension_list = array_filter(preg_split('/\s+/', $field_definition->getSetting('file_extensions')));
 
-    $extensionList = array_filter(preg_split('/\s+/', $field_definition->getSetting('file_extensions')));
-
-    foreach ($extensionList as $extension) {
-      $mimeType = $extension_mime_type_guesser->guess('fakedFile.' . $extension);
+    foreach ($extension_list as $extension) {
+      $mime_type = $extension_mime_type_guesser->guess('fakedFile.' . $extension);
 
-      if (static::getMimeTypeType($mimeType) == static::APPLICABLE_MIME_TYPE) {
+      if (static::mimeTypeApplies($mime_type)) {
         return TRUE;
       }
     }
@@ -144,10 +136,10 @@
    */
   public function settingsSummary() {
     $summary = [];
-    $summary[] = $this->t('Controls: %controls', array('%controls' => $this->getSetting('controls') ? $this->t('visible') : $this->t('hidden')));
-    $summary[] = $this->t('Autoplay: %autoplay', array('%autoplay' => $this->getSetting('autoplay') ? $this->t('yes') : $this->t('no')));
-    $summary[] = $this->t('Loop: %loop', array('%loop' => $this->getSetting('loop') ? $this->t('yes') : $this->t('no')));
-    $summary[] = $this->t('Multiple files: %multiple', array('%multiple' => $this->getSetting('multiple_file_behavior')));
+    $summary[] = $this->t('Controls: %controls', ['%controls' => $this->getSetting('controls') ? $this->t('visible') : $this->t('hidden')]);
+    $summary[] = $this->t('Autoplay: %autoplay', ['%autoplay' => $this->getSetting('autoplay') ? $this->t('yes') : $this->t('no')]);
+    $summary[] = $this->t('Loop: %loop', ['%loop' => $this->getSetting('loop') ? $this->t('yes') : $this->t('no')]);
+    $summary[] = $this->t('Multiple files: %multiple', ['%multiple' => $this->getSetting('multiple_file_behavior')]);
     return $summary;
   }
 
@@ -155,7 +147,7 @@
    * {@inheritdoc}
    */
   public function viewElements(FieldItemListInterface $items, $langcode) {
-    $elements = array();
+    $elements = [];
 
     $source_files = $this->getSourceFiles($items, $langcode);
 
@@ -165,11 +157,11 @@
 
     $attributes = $this->prepareAttributes();
     foreach ($source_files as $delta => $files) {
-      $elements[$delta] = array(
-        '#theme' => 'file_' . static::APPLICABLE_MIME_TYPE,
+      $elements[$delta] = [
+        '#theme' => 'file_' . static::getMimeType(),
         '#attributes' => $attributes,
         '#files' => $files,
-      );
+      ];
       foreach ($files as $file) {
         $this->renderer->addCacheableDependency($elements[$delta], $file['file']);
       }
@@ -182,13 +174,14 @@
    * Prepare the attributes according to the settings.
    *
    * @param array $additional_attributes
-   *   Additional attributes for preparing.
+   *   Additional attributes for preparing the html tag attributes.
    *
-   * @return Attribute
+   * @return \Drupal\Core\Template\Attribute
+   *   Container with all the attributes for the html tag.
    */
   protected function prepareAttributes(array $additional_attributes = []) {
     $attributes = new Attribute();
-    foreach (array('controls', 'autoplay', 'loop') + $additional_attributes as $attribute) {
+    foreach (['controls', 'autoplay', 'loop'] + $additional_attributes as $attribute) {
       if ($this->getSetting($attribute)) {
         $attributes->setAttribute($attribute, $attribute);
       }
@@ -197,17 +190,17 @@
   }
 
   /**
-   * Returns the first part of the mimetype of the file.
+   * Check if given mimetype applies to formatter one.
    *
    * @param string $mimeType
    *   The full mimeType.
    *
-   * @return string
-   *   The last part of a mimetype.
+   * @return bool
+   *   Mimetype applies or not.
    */
-  protected static function getMimeTypeType($mimeType) {
+  protected static function mimeTypeApplies($mimeType) {
     list($type) = explode('/', $mimeType, 2);
-    return $type;
+    return ($type == static::getMimeType());
   }
 
   /**
@@ -228,23 +221,23 @@
     // Because we can have the files grouped in a single media tag, we do a
     // grouping in case the multiple file behavior is not 'tags'.
     foreach ($this->getEntitiesToView($items, $langcode) as $file) {
-      if (static::getMimeTypeType($file->getMimeType()) == static::APPLICABLE_MIME_TYPE) {
+      if (static::mimeTypeApplies($file->getMimeType())) {
         $source_attributes = new Attribute();
         $source_attributes->setAttribute('src', file_create_url($file->getFileUri()));
         $source_attributes->setAttribute('type', $file->getMimeType());
         if ($multiple_file_behavior == 'tags') {
-          $source_files[] = array(
-            array(
+          $source_files[] = [
+            [
               'file' => $file,
-              'source_attributes' => $source_attributes
-            )
-          );
+              'source_attributes' => $source_attributes,
+            ],
+          ];
         }
         else {
-          $source_files[0][] = array(
+          $source_files[0][] = [
             'file' => $file,
-            'source_attributes' => $source_attributes
-          );
+            'source_attributes' => $source_attributes,
+          ];
         }
       }
     }
diff -u b/core/modules/file/src/Plugin/Field/FieldFormatter/FileVideoFormatter.php b/core/modules/file/src/Plugin/Field/FieldFormatter/FileVideoFormatter.php
--- b/core/modules/file/src/Plugin/Field/FieldFormatter/FileVideoFormatter.php
+++ b/core/modules/file/src/Plugin/Field/FieldFormatter/FileVideoFormatter.php
@@ -2,9 +2,7 @@
 
 namespace Drupal\file\Plugin\Field\FieldFormatter;
 
-use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Form\FormStateInterface;
-use Drupal\Core\Template\Attribute;
 
 /**
  * Plugin implementation of the 'file_video' formatter.
@@ -23,7 +21,9 @@
   /**
    * {@inheritdoc}
    */
-  const APPLICABLE_MIME_TYPE = 'video';
+  public static function getMimeType() {
+    return 'video';
+  }
 
   /**
    * {@inheritdoc}
@@ -42,27 +42,27 @@
   public function settingsForm(array $form, FormStateInterface $form_state) {
     $element = parent::settingsForm($form, $form_state);
 
-    $element['muted'] = array(
+    $element['muted'] = [
       '#title' => $this->t('Muted'),
       '#type' => 'checkbox',
       '#default_value' => $this->getSetting('muted'),
-    );
-    $element['width'] = array(
+    ];
+    $element['width'] = [
       '#type' => 'textfield',
       '#title' => $this->t('Width'),
       '#default_value' => $this->getSetting('width'),
       '#size' => 5,
       '#maxlength' => 5,
       '#field_suffix' => $this->t('pixels'),
-    );
-    $element['height'] = array(
+    ];
+    $element['height'] = [
       '#type' => 'textfield',
       '#title' => $this->t('Height'),
       '#default_value' => $this->getSetting('height'),
       '#size' => 5,
       '#maxlength' => 5,
       '#field_suffix' => $this->t('pixels'),
-    );
+    ];
 
     return $element;
   }
@@ -72,14 +72,14 @@
    */
   public function settingsSummary() {
     $summary = parent::settingsSummary();
-    $summary[] = $this->t('Muted: %muted', array('%muted' => $this->getSetting('muted') ? $this->t('yes') : $this->t('no')));
+    $summary[] = $this->t('Muted: %muted', ['%muted' => $this->getSetting('muted') ? $this->t('yes') : $this->t('no')]);
     $width = $this->getSetting('width');
     $height = $this->getSetting('height');
     if ($width && $height) {
-      $summary[] = $this->t('Size: %width x %height pixels', array(
+      $summary[] = $this->t('Size: %width x %height pixels', [
         '%width' => $this->getSetting('width'),
         '%height' => $this->getSetting('height'),
-      ));
+      ]);
     }
     return $summary;
   }
@@ -88,7 +88,6 @@
    * {@inheritdoc}
    */
   protected function prepareAttributes(array $additional_attributes = []) {
-
     $video_attributes = parent::prepareAttributes(['muted']);
     $width = $this->getSetting('width');
     $height = $this->getSetting('height');
diff -u b/core/modules/file/tests/src/Kernel/Formatter/FileVideoFormatterTest.php b/core/modules/file/tests/src/Kernel/Formatter/FileVideoFormatterTest.php
--- b/core/modules/file/tests/src/Kernel/Formatter/FileVideoFormatterTest.php
+++ b/core/modules/file/tests/src/Kernel/Formatter/FileVideoFormatterTest.php
@@ -54,7 +54,7 @@
     $this->installSchema('file', array('file_usage'));
 
     $entityType = 'entity_test';
-    $bundle = $this->entityType;
+    $bundle = $entityType;
     $this->fieldName = Unicode::strtolower($this->randomMachineName());
 
     FieldStorageConfig::create(array(
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/file/src/Plugin/Field/FieldFormatter/FileMediaFormatterInterface.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace Drupal\file\Plugin\Field\FieldFormatter;
+
+/**
+ * Defines getter and setter methods for FileMediaFormatters.
+ *
+ * @package Drupal\file\Plugin\Field\FieldFormatter
+ */
+interface FileMediaFormatterInterface {
+
+  /**
+   * The applicable mimetype for a formatter.
+   */
+  public static function getMimeType();
+
+}