Update the window labels if they change in overview mode.

ash/wm/overview/window_selector_window.cc

 // Copyright 2013 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/overview/window_selector_window.h"
 
 #include "ash/screen_util.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/wm/overview/scoped_transform_overview_window.h"
 #include "grit/ash_resources.h"
 #include "ui/aura/window.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/transform.h"
 #include "ui/views/controls/button/image_button.h"
 #include "ui/views/widget/widget.h"
 
 namespace ash {
 
 WindowSelectorWindow::WindowSelectorWindow(aura::Window* window)
     : transform_window_(window) {
+  window->AddObserver(this);
 }
 
 WindowSelectorWindow::~WindowSelectorWindow() {
+  if (transform_window_.window())
+    transform_window_.window()->RemoveObserver(this);
 }
 
 aura::Window* WindowSelectorWindow::GetRootWindow() {
   return transform_window_.window()->GetRootWindow();
 }
 
 bool WindowSelectorWindow::HasSelectableWindow(const aura::Window* window) {
   return transform_window_.window() == window;
 }
 
 bool WindowSelectorWindow::Contains(const aura::Window* target) {
   return transform_window_.Contains(target);
 }
 
 void WindowSelectorWindow::RestoreWindowOnExit(aura::Window* window) {
   transform_window_.RestoreWindowOnExit();
 }
 
 aura::Window* WindowSelectorWindow::SelectionWindow() {
   return transform_window_.window();
 }
 
 void WindowSelectorWindow::RemoveWindow(const aura::Window* window) {
   DCHECK_EQ(transform_window_.window(), window);
+  transform_window_.window()->RemoveObserver(this);
   transform_window_.OnWindowDestroyed();
   WindowSelectorItem::RemoveWindow(window);
 }
 
 bool WindowSelectorWindow::empty() const {
   return transform_window_.window() == NULL;
 }
 
 void WindowSelectorWindow::PrepareForOverview() {
   transform_window_.PrepareForOverview();
 }
 
 void WindowSelectorWindow::SetItemBounds(aura::Window* root_window,
                                          const gfx::Rect& target_bounds,
                                          bool animate) {
   gfx::Rect src_rect = transform_window_.GetBoundsInScreen();
   set_bounds(ScopedTransformOverviewWindow::
         ShrinkRectToFitPreservingAspectRatio(src_rect, target_bounds));
   transform_window_.SetTransform(root_window,
       ScopedTransformOverviewWindow::GetTransformForRect(src_rect, bounds()),
       animate);
 }
 
 }  // namespace ash