Make GetRootWindow() return a Window instead of a RootWindow.

ash/scoped_target_root_window.h

Index: ash/scoped_target_root_window.h
diff --git a/ash/scoped_target_root_window.h b/ash/scoped_target_root_window.h
index ab695be6b6e1f9f52532f7c5ec837ccfb71aa23b..0e7a8b18d7ca238b40da0c8705ae5e93c83854da 100644
--- a/ash/scoped_target_root_window.h
+++ b/ash/scoped_target_root_window.h
@@ -7,7 +7,7 @@
 #include "base/basictypes.h"
 
 namespace aura {
-class RootWindow;
+class Window;
 }
 
 namespace ash {
@@ -20,7 +20,7 @@ namespace internal {
 // a new window using launcher's icon.
 class ScopedTargetRootWindow {
  public:
-  explicit ScopedTargetRootWindow(aura::RootWindow* root_window);
+  explicit ScopedTargetRootWindow(aura::Window* root_window);
   ~ScopedTargetRootWindow();
 
  private: