Move the concept of Activation to the Shell.

ui/aura_shell/shadow_controller.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 "ui/aura_shell/shadow_controller.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/client/shadow_types.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/window.h"
 #include "ui/aura_shell/shadow.h"
 
 using std::make_pair;
 
 namespace aura_shell {
 namespace internal {
 
 ShadowController::ShadowController() {
-  aura::RootWindow::GetInstance()->AddObserver(this);
+  aura::RootWindow::GetInstance()->AddRootWindowObserver(this);
 }
 
 ShadowController::~ShadowController() {
   for (WindowShadowMap::const_iterator it = window_shadows_.begin();
        it != window_shadows_.end(); ++it) {
     it->first->RemoveObserver(this);
   }
-  aura::RootWindow::GetInstance()->RemoveObserver(this);
+  aura::RootWindow::GetInstance()->RemoveRootWindowObserver(this);
 }
 
 void ShadowController::OnWindowInitialized(aura::Window* window) {
   window->AddObserver(this);
   HandlePossibleShadowVisibilityChange(window);
 }
 
 void ShadowController::OnWindowPropertyChanged(aura::Window* window,
                                                const char* name,
                                                void* old) {
@@ skipping 46 matching lines @@
   window_shadows_.insert(make_pair(window, shadow));
 
   shadow->Init();
   shadow->SetContentBounds(gfx::Rect(window->bounds().size()));
   shadow->layer()->SetVisible(ShouldShowShadowForWindow(window));
   window->layer()->Add(shadow->layer());
 }
 
 }  // namespace internal
 }  // namespace aura_shell