CC Animations: Make ui::LayerAnimator a LayerAnimationEventObserver (instead of ui::Layer)

ui/compositor/layer_animator_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/compositor/layer_animator.h"
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/stringprintf.h"
@@ skipping 2434 matching lines @@
   collection->OnAnimationStep(null);
   EXPECT_TRUE(collection->last_tick_time().is_null());
 
   // Adding an animator to the collection should update the last tick time.
   collection->StartAnimator(layer.GetAnimator());
   EXPECT_TRUE(collection->HasActiveAnimators());
   EXPECT_FALSE(collection->last_tick_time().is_null());
 
   collection->StopAnimator(layer.GetAnimator());
   EXPECT_FALSE(collection->HasActiveAnimators());
+
+  animator->SetDelegate(nullptr);
 }
 
 TEST(LayerAnimatorTest, AnimatorStartedCorrectly) {
   Layer layer;
   LayerAnimatorTestController test_controller(layer.GetAnimator());
   LayerAnimator* animator = test_controller.animator();
   ASSERT_FALSE(animator->is_started_);
 
   TestLayerAnimationDelegate test_delegate;
   animator->SetDelegate(&test_delegate);
@@ skipping 330 matching lines @@
   EXPECT_EQ(observer.last_ended_sequence(), nullptr);
   EXPECT_EQ(observer.last_detached_sequence(), first_sequence);
 
   EXPECT_TRUE(observer.AbortedEpochIsBeforeDetachedEpoch());
   EXPECT_TRUE(observer.AbortedEpochIsBeforeStartedEpoch());
   EXPECT_TRUE(observer.AttachedEpochIsBeforeScheduledEpoch());
   EXPECT_TRUE(observer.ScheduledEpochIsBeforeStartedEpoch());
 }
 
 }  // namespace ui