Add MetalayerMode to the palette.

ash/palette_delegate.h

 // Copyright 2016 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_PALETTE_DELEGATE_H_
 #define ASH_PALETTE_DELEGATE_H_
 
 #include "ash/ash_export.h"
 #include "base/callback.h"
 #include "base/callback_list.h"
@@ skipping 36 matching lines @@
   virtual void TakeScreenshot() = 0;
 
   // Take a screenshot of a user-selected region. |done| is called when the
   // partial screenshot session has finished; a screenshot may or may not have
   // been taken.
   virtual void TakePartialScreenshot(const base::Closure& done) = 0;
 
   // Cancels any active partial screenshot session.
   virtual void CancelPartialScreenshot() = 0;
 
+  // Returns true if the metalayer is available.
+  virtual bool IsMetalayerSupported() = 0;
+
+  // Shows the metalayer.
+  // |closed| will be invoked when the metalayer is closed or
+  // if the metalayer could not be shown.
+  virtual void ShowMetalayer(const base::Closure& closed) = 0;
+
+  // Hides the metalayer.
+  virtual void HideMetalayer() = 0;
+
  private:
   DISALLOW_ASSIGN(PaletteDelegate);
 };
 
 }  // namespace ash
 
 #endif  // ASH_PALETTE_DELEGATE_H_