Update the window labels if they change in overview mode.

ui/aura/window_observer.h

 // 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.
 
 #ifndef UI_AURA_WINDOW_OBSERVER_H_
 #define UI_AURA_WINDOW_OBSERVER_H_
 
 #include "base/basictypes.h"
+#include "base/strings/string16.h"
 #include "ui/aura/aura_export.h"
 
 namespace gfx {
 class Rect;
 }  // namespace gfx
 
 namespace aura {
 
 class Window;
 
@@ skipping 86 matching lines @@
 
   // Called when a Window has been added to a RootWindow.
   virtual void OnWindowAddedToRootWindow(Window* window) {}
 
   // Called when a Window is about to be removed from a root Window.
   // |new_root| contains the new root Window if it is being added to one
   // atomically.
   virtual void OnWindowRemovingFromRootWindow(Window* window,
                                               Window* new_root) {}
 
+  // Called when the window title has changed.
+  virtual void OnWindowTitleChanged(Window* window,
+                                    const base::string16& new_title) {}

[flackr, 2014/06/24 17:10:51]

nit: since we're not passing the old title I would just call this title instead
of new_title.

[Nina, 2014/06/24 18:36:28]

Done.

+
  protected:
   virtual ~WindowObserver();
 
  private:
   friend class Window;
 
   // Called when this is added as an observer on |window|.
   void OnObservingWindow(Window* window);
 
   // Called when this is removed from the observers on |window|.
   void OnUnobservingWindow(Window* window);
 
   // Tracks the number of windows being observed to track down
   // http://crbug.com/365364.
   int observing_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowObserver);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_OBSERVER_H_