aura: Reland r266681 to debug WindowObserver crashes.

ui/aura/window.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/window.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 626 matching lines @@
   gfx::Point point_in_root(point_in_window);
   ConvertPointToTarget(this, root_window, &point_in_root);
   root_window->GetHost()->MoveCursorTo(point_in_root);
 }
 
 gfx::NativeCursor Window::GetCursor(const gfx::Point& point) const {
   return delegate_ ? delegate_->GetCursor(point) : gfx::kNullCursor;
 }
 
 void Window::AddObserver(WindowObserver* observer) {
+  observer->OnObservingWindow(this);
   observers_.AddObserver(observer);
 }
 
 void Window::RemoveObserver(WindowObserver* observer) {
+  observer->OnUnobservingWindow(this);
   observers_.RemoveObserver(observer);
 }
 
 bool Window::HasObserver(WindowObserver* observer) {
   return observers_.HasObserver(observer);
 }
 
 bool Window::ContainsPointInRoot(const gfx::Point& point_in_root) const {
   const Window* root_window = GetRootWindow();
   if (!root_window)
@@ skipping 765 matching lines @@
       return window;
     if (offset)
       *offset += window->bounds().OffsetFromOrigin();
   }
   if (offset)
     *offset = gfx::Vector2d();
   return NULL;
 }
 
 }  // namespace aura