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

ash/wm/screen_dimmer_unittest.cc

 // 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.
 
 #include "ash/wm/screen_dimmer.h"
 
 #include "ash/root_window_controller.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
 #include "base/basictypes.h"
@@ skipping 53 matching lines @@
   dimmer_->SetDimming(true);
   ui::Layer* dimming_layer = test_api_->layer();
   ASSERT_TRUE(dimming_layer != NULL);
   ui::Layer* root_layer = Shell::GetPrimaryRootWindow()->layer();
   EXPECT_EQ(gfx::Rect(root_layer->bounds().size()).ToString(),
             dimming_layer->bounds().ToString());
 
   // When we resize the root window, the dimming layer should be resized to
   // match.
   gfx::Size kNewSize(400, 300);
-  Shell::GetPrimaryRootWindow()->SetHostSize(kNewSize);
+  Shell::GetPrimaryRootWindow()->GetDispatcher()->SetHostSize(kNewSize);
   EXPECT_EQ(kNewSize.ToString(), dimming_layer->bounds().size().ToString());
 }
 
 }  // namespace test
 }  // namespace ash