Introduce XGetImage() for GrabWindowSnapshot() in ChromeOS.

ui/aura/root_window_host_linux.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_LINUX_H_
 #define UI_AURA_ROOT_WINDOW_HOST_LINUX_H_
 #pragma once
 
 #include <X11/Xlib.h>
 
@@ skipping 32 matching lines @@
   virtual gfx::Point GetLocationOnNativeScreen() const OVERRIDE;
   virtual void SetCapture() OVERRIDE;
   virtual void ReleaseCapture() OVERRIDE;
   virtual void SetCursor(gfx::NativeCursor cursor_type) OVERRIDE;
   virtual void ShowCursor(bool show) OVERRIDE;
   virtual gfx::Point QueryMouseLocation() OVERRIDE;
   virtual bool ConfineCursorToRootWindow() OVERRIDE;
   virtual void UnConfineCursor() OVERRIDE;
   virtual void MoveCursorTo(const gfx::Point& location) OVERRIDE;
   virtual void SetFocusWhenShown(bool focus_when_shown) OVERRIDE;
+  virtual bool GrabSnapshot(
+      const gfx::Rect& snapshot_bounds,
+      std::vector<unsigned char>* png_representation) OVERRIDE;
   virtual void PostNativeEvent(const base::NativeEvent& event) OVERRIDE;
 
   // Returns true if there's an X window manager present... in most cases.  Some
   // window managers (notably, ion3) don't implement enough of ICCCM for us to
   // detect that they're there.
   bool IsWindowManagerPresent();
 
   // Sets the cursor on |xwindow_| to |cursor|.  Does not check or update
   // |current_cursor_|.
   void SetCursorInternal(gfx::NativeCursor cursor);
@@ skipping 28 matching lines @@
 
   class ImageCursors;
   scoped_ptr<ImageCursors> image_cursors_;
 
   DISALLOW_COPY_AND_ASSIGN(RootWindowHostLinux);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_ROOT_WINDOW_HOST_LINUX_H_