Adds keyboard functionality for videos.

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

Index: third_party/WebKit/Source/modules/media_controls/elements/MediaControlVolumeSliderElement.h
diff --git a/third_party/WebKit/Source/modules/media_controls/elements/MediaControlVolumeSliderElement.h b/third_party/WebKit/Source/modules/media_controls/elements/MediaControlVolumeSliderElement.h
index 1bb2b658c895001bffb37081e38a2b508caee8d5..2e3c434bd612cad2f02e34f71556756cc12e258b 100644
--- a/third_party/WebKit/Source/modules/media_controls/elements/MediaControlVolumeSliderElement.h
+++ b/third_party/WebKit/Source/modules/media_controls/elements/MediaControlVolumeSliderElement.h
@@ -23,6 +23,8 @@ class MediaControlVolumeSliderElement final : public MediaControlInputElement {
   bool WillRespondToMouseMoveEvents() override;
   bool WillRespondToMouseClickEvents() override;
 
+  void OnMediaKeyboardEvent(Event* event) { DefaultEventHandler(event); }
+
  private:
   void DefaultEventHandler(Event*) override;
   bool KeepEventInNode(Event*) override;