Compact layout mananger animates windows rather than the default container layer.

ui/gfx/compositor/scoped_layer_animation_settings.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/gfx/compositor/scoped_layer_animation_settings.h"
 
 #include "ui/gfx/compositor/layer_animation_observer.h"
 #include "ui/gfx/compositor/layer_animator.h"
 
 namespace {
 
 static const base::TimeDelta kDefaultTransitionDuration =
     base::TimeDelta::FromMilliseconds(200);
 
 } // namespace;
 
 namespace ui {
 
 ScopedLayerAnimationSettings::ScopedLayerAnimationSettings(
     LayerAnimator* animator)
     : animator_(animator),
-      old_transition_duration_(animator->transition_duration_) {
+      old_transition_duration_(animator->transition_duration_),
+      old_preemption_strategy_(animator->preemption_strategy_) {
   SetTransitionDuration(kDefaultTransitionDuration);
 }
 
 ScopedLayerAnimationSettings::~ScopedLayerAnimationSettings() {
   animator_->transition_duration_ = old_transition_duration_;
+  animator_->preemption_strategy_ = old_preemption_strategy_;
 
   for (std::set<ImplicitAnimationObserver*>::const_iterator i =
        observers_.begin(); i != observers_.end(); ++i) {
     animator_->observers_.RemoveObserver(*i);
     (*i)->SetActive(true);
   }
 }
 
 void ScopedLayerAnimationSettings::AddObserver(
     ImplicitAnimationObserver* observer) {
   observers_.insert(observer);
   animator_->AddObserver(observer);
 }
 
 void ScopedLayerAnimationSettings::SetTransitionDuration(
     base::TimeDelta duration) {
   animator_->transition_duration_ = duration;
 }
 
+void ScopedLayerAnimationSettings::SetPreemptionStrategy(
+    LayerAnimator::PreemptionStrategy strategy) {
+  animator_->preemption_strategy_ = strategy;
+}
+
 }  // namespace ui