[ash-md] Fixed ShelfBackgroundAnimator to not snap target values when being preempted.

ash/common/shelf/shelf_background_animator.cc

 // Copyright 2016 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/shelf/shelf_background_animator.h"
 
 #include <algorithm>
 
 #include "ash/animation/animation_change_type.h"
 #include "ash/common/shelf/shelf_background_animator_observer.h"
@@ skipping 80 matching lines @@
   DCHECK_EQ(animation, animator_.get());
   SetAnimationValues(animation->GetCurrentValue());
 }
 
 void ShelfBackgroundAnimator::AnimationEnded(const gfx::Animation* animation) {
   DCHECK_EQ(animation, animator_.get());
   SetAnimationValues(animation->GetCurrentValue());
   animator_.reset();
 }
 
-void ShelfBackgroundAnimator::AnimationCanceled(
-    const gfx::Animation* animation) {
-  DCHECK_EQ(animation, animator_.get());
-  SetAnimationValues(animator_->IsShowing() ? 1.0 : 0.0);
-  // Animations are only cancelled when they are being pre-empted so we don't
-  // destroy the |animator_| because it may be re-used immediately.
-}
-
 void ShelfBackgroundAnimator::OnWallpaperDataChanged() {}
 
 void ShelfBackgroundAnimator::OnWallpaperColorsChanged() {
   AnimateBackground(target_background_type_, AnimationChangeType::ANIMATE);
 }
 
 void ShelfBackgroundAnimator::OnBackgroundTypeChanged(
     ShelfBackgroundType background_type,
     AnimationChangeType change_type) {
   PaintBackground(background_type, change_type);
@@ skipping 117 matching lines @@
 
 void ShelfBackgroundAnimator::SetAnimationValues(double t) {
   DCHECK_GE(t, 0.0);
   DCHECK_LE(t, 1.0);
   shelf_background_values_.UpdateCurrentValues(t);
   item_background_values_.UpdateCurrentValues(t);
   NotifyObservers();
 }
 
 }  // namespace ash