Make sure WindowObservers are removed from window before destruction

ash/wm/solo_window_tracker_unittest.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/solo_window_tracker.h"
 
 #include "ash/ash_constants.h"
 #include "ash/ash_switches.h"
 #include "ash/root_window_controller.h"
 #include "ash/screen_ash.h"
@@ skipping 11 matching lines @@
 #include "ui/base/hit_test.h"
 #include "ui/gfx/screen.h"
 
 namespace ash {
 
 namespace {
 
 class WindowRepaintChecker : public aura::WindowObserver {
  public:
   explicit WindowRepaintChecker(aura::Window* window)
-      : is_paint_scheduled_(false) {
-    window->AddObserver(this);
+      : window_(window),
+        is_paint_scheduled_(false) {
+    window_->AddObserver(this);
   }
+
   virtual ~WindowRepaintChecker() {
+    if (window_)
+      window_->RemoveObserver(this);
   }
 
   bool IsPaintScheduledAndReset() {
     bool result = is_paint_scheduled_;
     is_paint_scheduled_ = false;
     return result;
   }
 
  private:
   // aura::WindowObserver overrides:
   virtual void OnWindowPaintScheduled(aura::Window* window,
                                       const gfx::Rect& region) OVERRIDE {
     is_paint_scheduled_ = true;
   }
-  virtual void OnWindowDestroying(aura::Window* window) OVERRIDE {
-    window->RemoveObserver(this);
+  virtual void OnWindowDestroyed(aura::Window* window) OVERRIDE {
+    DCHECK_EQ(window_, window);
+    window_ = NULL;
   }
 
+  aura::Window* window_;
   bool is_paint_scheduled_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowRepaintChecker);
 };
 
 }  // namespace
 
 class SoloWindowTrackerTest : public test::AshTestBase {
  public:
   SoloWindowTrackerTest() {
@@ skipping 350 matching lines @@
   w.reset();
   EXPECT_EQ(NULL, GetWindowWithSoloHeaderInPrimary());
 
   // Recreate another window again.
   w.reset(CreateWindowInPrimary());
   w->Show();
   EXPECT_EQ(w.get(), GetWindowWithSoloHeaderInPrimary());
 }
 
 }  // namespace ash