Adds keyboard functionality for videos.

third_party/WebKit/Source/core/html/shadow/MediaControlElements.h

 /*
  * Copyright (C) 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 25 matching lines @@
 
 class CORE_EXPORT MediaControlVolumeSliderElement final
     : public MediaControlInputElement {
  public:
   static MediaControlVolumeSliderElement* Create(MediaControls&);
 
   bool WillRespondToMouseMoveEvents() override;
   bool WillRespondToMouseClickEvents() override;
   void SetVolume(double);
 
+  void OnMediaKeyboardEvent(Event* event) { DefaultEventHandler(event); }
+
  private:
   explicit MediaControlVolumeSliderElement(MediaControls&);
 
   void DefaultEventHandler(Event*) override;
   bool KeepEventInNode(Event*) override;
 };
 
 }  // namespace blink
 
 #endif  // MediaControlElements_h