Replaced BackgroundAnimator with ShelfBackgroundAnimator.

ash/common/wm/background_animator.cc

Index: ash/common/wm/background_animator.cc
diff --git a/ash/common/wm/background_animator.cc b/ash/common/wm/background_animator.cc
index b8596fb2760f91933d828cadf0c51269cc526e56..ed13bbba6c9001758c3e25fe7fcadc87da7d41ef 100644
--- a/ash/common/wm/background_animator.cc
+++ b/ash/common/wm/background_animator.cc
@@ -29,6 +29,10 @@ void BackgroundAnimator::SetDuration(int time_in_ms) {
   animation_.SetSlideDuration(time_in_ms);
 }
 
+void BackgroundAnimator::Stop() {
+  animation_.Stop();
+}
+
 void BackgroundAnimator::SetPaintsBackground(
     bool value,
     BackgroundAnimatorChangeType type) {
@@ -38,6 +42,7 @@ void BackgroundAnimator::SetPaintsBackground(
   if (type == BACKGROUND_CHANGE_IMMEDIATE && !animation_.is_animating()) {
     animation_.Reset(value ? 1.0f : 0.0f);
     AnimationProgressed(&animation_);
+    AnimationEnded(&animation_);
     return;
   }
   if (paints_background_)
@@ -51,7 +56,11 @@ void BackgroundAnimator::AnimationProgressed(const gfx::Animation* animation) {
   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