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

ui/aura/root_window_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 "ui/aura/root_window.h"
 
 #include <vector>
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/aura/client/event_client.h"
@@ skipping 974 matching lines @@
 
   virtual ~RepostGestureEventRecorder() {}
 
   virtual void OnGestureEvent(ui::GestureEvent* event) OVERRIDE {
     EXPECT_EQ(reposted_ ? repost_target_ : repost_source_, event->target());
     if (event->type() == ui::ET_GESTURE_TAP_DOWN) {
       if (!reposted_) {
         EXPECT_NE(repost_target_, event->target());
         reposted_ = true;
         events().clear();
-        repost_target_->GetRootWindow()->RepostEvent(*event);
+        repost_target_->GetDispatcher()->RepostEvent(*event);
         // Ensure that the reposted gesture event above goes to the
         // repost_target_;
         repost_source_->GetRootWindow()->RemoveChild(repost_source_);
         return;
       }
     }
     EventFilterRecorder::OnGestureEvent(event);
   }
 
   // Ignore mouse events as they don't fire at all times. This causes
@@ skipping 168 matching lines @@
     // Owned by RootWindow.
     Window* w1 = CreateNormalWindow(1, root_window.get(), NULL);
     w1->AddObserver(&observer);
   }
   EXPECT_TRUE(got_destroying);
   EXPECT_TRUE(has_valid_root);
 }
 
 }  // namespace aura