Ash: Support "Next Song", "Previous Song", "Play/Pause" Multi Media buttons

ash/shell_delegate.h

Index: ash/shell_delegate.h
diff --git a/ash/shell_delegate.h b/ash/shell_delegate.h
index 8029e1b9686ac0581fd26bf3e987d3b88a893a50..7b7d0971e628d1b3a88dcb25a5960c76c149d29a 100644
--- a/ash/shell_delegate.h
+++ b/ash/shell_delegate.h
@@ -137,6 +137,15 @@ class ASH_EXPORT ShellDelegate {
 
   // Records that the user performed an action.
   virtual void RecordUserMetricsAction(UserMetricsAction action) = 0;
+
+  // Handles the Next Track Media shortcut key.
+  virtual void HandleMediaNextTrack() = 0;
+
+  // Handles the Play/Pause Toggle Media shortcut key.
+  virtual void HandleMediaPlayPause() = 0;
+
+  // Handles the Previous Track Media shortcut key.
+  virtual void HandleMediaPrevTrack() = 0;
 };
 
 }  // namespace ash