chromeos: Add operations to monitor the screen orientation.

chrome/browser/ui/touch/frame/touch_browser_frame_view.cc

 // Copyright (c) 2011 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.
 
 #include "chrome/browser/ui/touch/frame/touch_browser_frame_view.h"
 
 #include "chrome/browser/ui/touch/animation/screen_rotation_setter.h"
 #include "chrome/browser/ui/touch/keyboard/keyboard_manager.h"
 #include "views/controls/button/image_button.h"
 #include "views/desktop/desktop_window_view.h"
@@ skipping 91 matching lines @@
     to_rotate = widget->GetRootView();
   }
 
   if (!initialized_screen_rotation_) {
     to_rotate->SetPaintToLayer(true);
     to_rotate->SetLayerPropertySetter(
         ScreenRotationSetterFactory::Create(to_rotate));
     initialized_screen_rotation_ = true;
   }
 
-  ui::Transform xform = SideToTransform(change.upward,
-                                        to_rotate->GetTransform(),
-                                        to_rotate->size());
-
-  to_rotate->SetTransform(xform);
+  const ui::Transform& old_xform = to_rotate->GetTransform();
+  const ui::Transform& new_xform = SideToTransform(change.upward,
+                                                   old_xform,
+                                                   to_rotate->size());
+  if (old_xform != new_xform)
+    to_rotate->SetTransform(new_xform);
 }
-