Introduce XGetImage() for GrabWindowSnapshot() in ChromeOS.

BUG=119492
TEST=manually done

Review URL: https://chromiumcodereview.appspot.com/10386124

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@137556 0039d316-1c4b-4281-b951-d872f2087c98
RootWindowHostLinux::~RootWindowHostLinux() {
  static_cast<DispatcherLinux*>(Env::GetInstance()->GetDispatcher())->
      WindowDispatcherDestroying(xwindow_);

  UnConfineCursor();

  XDestroyWindow(xdisplay_, xwindow_);

  ui::GetXCursor(ui::kCursorClearXCursorCache);

  XFreeCursor(xdisplay_, invisible_cursor_);
}

RootWindowHostLinux::~RootWindowHostLinux() {
  static_cast<DispatcherLinux*>(Env::GetInstance()->GetDispatcher())->
      WindowDispatcherDestroying(xwindow_);

  UnConfineCursor();

  XDestroyWindow(xdisplay_, xwindow_);

  ui::GetXCursor(ui::kCursorClearXCursorCache);

  XFreeCursor(xdisplay_, invisible_cursor_);
}
