aura: Reland r266681 to debug WindowObserver crashes.

ui/aura/window_unittest.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 <string>
 #include <utility>
 #include <vector>
 
@@ skipping 2211 matching lines @@
 TEST_F(WindowTest, RootWindowSetWhenReparenting) {
   Window parent1(NULL);
   parent1.Init(aura::WINDOW_LAYER_NOT_DRAWN);
   Window parent2(NULL);
   parent2.Init(aura::WINDOW_LAYER_NOT_DRAWN);
   ParentWindow(&parent1);
   ParentWindow(&parent2);
   parent1.SetBounds(gfx::Rect(10, 10, 300, 300));
   parent2.SetBounds(gfx::Rect(20, 20, 300, 300));
 
+  BoundsChangedWindowObserver observer;
   Window child(NULL);
   child.Init(aura::WINDOW_LAYER_NOT_DRAWN);
   child.SetBounds(gfx::Rect(5, 5, 100, 100));
   parent1.AddChild(&child);
 
   // We need animations to start in order to observe the bounds changes.
   ui::ScopedAnimationDurationScaleMode animation_duration_mode(
       ui::ScopedAnimationDurationScaleMode::NORMAL_DURATION);
   ui::ScopedLayerAnimationSettings settings1(child.layer()->GetAnimator());
   settings1.SetTransitionDuration(base::TimeDelta::FromMilliseconds(100));
   gfx::Rect new_bounds(gfx::Rect(35, 35, 50, 50));
   child.SetBounds(new_bounds);
 
-  BoundsChangedWindowObserver observer;
   child.AddObserver(&observer);
 
   // Reparenting the |child| will cause it to get moved. During this move
   // the window should still have root window set.
   parent2.AddChild(&child);
   EXPECT_TRUE(observer.root_set());
 
   // Animations should stop and the bounds should be as set before the |child|
   // got reparented.
   EXPECT_EQ(new_bounds.ToString(), child.GetTargetBounds().ToString());
@@ skipping 1086 matching lines @@
               BuildRootLayerTreeDescription(*root.layer()))
         << "layer tree doesn't match at " << i;
     EXPECT_EQ(data[i].expected_description,
               BuildRootWindowTreeDescription(root))
         << "window tree doesn't match at " << i;
   }
 }
 
 }  // namespace test
 }  // namespace aura