cros: Suspend media sessions with display off trigger by tablet power button

ash/shell_delegate.h

 // Copyright (c) 2012 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 ASH_SHELL_DELEGATE_H_
 #define ASH_SHELL_DELEGATE_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 120 matching lines @@
   // pref is set in local state, otherwise in user prefs.
   virtual void SetTouchscreenEnabledInPrefs(bool enabled,
                                             bool use_local_state) = 0;
 
   // Updates the enabled/disabled status of the touchscreen from prefs. Enabled
   // if both local state and user prefs are enabled, otherwise disabled.
   virtual void UpdateTouchscreenStatusFromPrefs() = 0;
 
   // Toggles the status of touchpad between enabled and disabled.
   virtual void ToggleTouchpad() {}
+
+  // Suspends all WebContents-associated media sessions to stop managed players.
+  virtual void SuspendMediaSessions() {}
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELL_DELEGATE_H_