Reland of "Apply Shelf/Dock opacity animations for the Material Design style."

ash/common/wm/background_animator.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 "ash/common/wm/background_animator.h"
 
 namespace ash {
 namespace {
 
 // Duration of the background animation.
@@ skipping 11 matching lines @@
       alpha_(min_alpha) {
   animation_.SetSlideDuration(kBackgroundDurationMS);
 }
 
 BackgroundAnimator::~BackgroundAnimator() {}
 
 void BackgroundAnimator::SetDuration(int time_in_ms) {
   animation_.SetSlideDuration(time_in_ms);
 }
 
+void BackgroundAnimator::Stop() {
+  animation_.Stop();
+}
+
 void BackgroundAnimator::SetPaintsBackground(
     bool value,
     BackgroundAnimatorChangeType type) {
   if (paints_background_ == value)
     return;
   paints_background_ = value;
   if (type == BACKGROUND_CHANGE_IMMEDIATE && !animation_.is_animating()) {
     animation_.Reset(value ? 1.0f : 0.0f);
     AnimationProgressed(&animation_);
+    AnimationEnded(&animation_);
     return;
   }
   if (paints_background_)
     animation_.Show();
   else
     animation_.Hide();
 }
 
 void BackgroundAnimator::AnimationProgressed(const gfx::Animation* animation) {
   int alpha = animation->CurrentValueBetween(min_alpha_, max_alpha_);
   if (alpha_ == alpha)
     return;
   alpha_ = alpha;
-  delegate_->UpdateBackground(alpha_);
+  delegate_->UpdateBackground(this, alpha_);
+}
+
+void BackgroundAnimator::AnimationEnded(const gfx::Animation* animation) {
+  delegate_->BackgroundAnimationEnded(this);
 }
 
 }  // namespace ash