Adds keyboard functionality for videos.

third_party/WebKit/Source/modules/media_controls/elements/MediaControlVolumeSliderElement.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MediaControlVolumeSliderElement_h
 #define MediaControlVolumeSliderElement_h
 
 #include "core/html/shadow/MediaControlElementTypes.h"
 
 namespace blink {
 
 class Event;
 class MediaControlsImpl;
 
 class MediaControlVolumeSliderElement final : public MediaControlInputElement {
  public:
   explicit MediaControlVolumeSliderElement(MediaControlsImpl&);
 
   // TODO: who calls this?
   void SetVolume(double);
 
   // MediaControlInputElement overrides.
   bool WillRespondToMouseMoveEvents() override;
   bool WillRespondToMouseClickEvents() override;
 
+  void OnMediaKeyboardEvent(Event* event) { DefaultEventHandler(event); }
+
  private:
   void DefaultEventHandler(Event*) override;
   bool KeepEventInNode(Event*) override;
 };
 
 }  // namespace blink
 
 #endif  // MediaControlVolumeSliderElement_h