Introduce XGetImage() for GrabWindowSnapshot() in ChromeOS.

ui/aura/root_window_host.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 UI_AURA_ROOT_WINDOW_HOST_H_
 #define UI_AURA_ROOT_WINDOW_HOST_H_
 #pragma once
 
+#include <vector>
+
 #include "base/message_loop.h"
 #include "ui/base/cursor/cursor.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace gfx {
 class Point;
 class Rect;
 class Size;
 }
 
@@ skipping 62 matching lines @@
   // Clips the cursor to the bounds of the root window until UnConfineCursor().
   virtual bool ConfineCursorToRootWindow() = 0;
   virtual void UnConfineCursor() = 0;
 
   // Moves the cursor to the specified location relative to the root window.
   virtual void MoveCursorTo(const gfx::Point& location) = 0;
 
   // Sets if the window should be focused when shown.
   virtual void SetFocusWhenShown(bool focus_when_shown) = 0;
 
+  // Grabs the window snapshot by using the platform-dependent APIs.
+  virtual bool GrabWindowSnapshot(
+      std::vector<unsigned char>* png_representation,
+      const gfx::Rect& snapshot_bounds) = 0;
+
   // Posts |native_event| to the platform's event queue.
 #if !defined(OS_MACOSX)
   virtual void PostNativeEvent(const base::NativeEvent& native_event) = 0;
 #endif
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_ROOT_WINDOW_HOST_H_