CC Animations: Make LayerAnimationController creation optional

cc/blink/web_layer_impl.cc

 // Copyright 2014 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 "cc/blink/web_layer_impl.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 44 matching lines @@
   layer_->SetLayerClient(this);
 }
 
 WebLayerImpl::WebLayerImpl(scoped_refptr<Layer> layer) : layer_(layer) {
   web_layer_client_ = nullptr;
   layer_->SetLayerClient(this);
 }
 
 WebLayerImpl::~WebLayerImpl() {
   layer_->ClearRenderSurface();
-  layer_->set_layer_animation_delegate(nullptr);
+  if (animation_delegate_adapter_.get())
+    layer_->set_layer_animation_delegate(nullptr);
   web_layer_client_ = nullptr;
 }
 
 // static
 bool WebLayerImpl::UsingPictureLayer() {
   return g_impl_side_painting_enabled;
 }
 
 // static
 void WebLayerImpl::SetImplSidePaintingEnabled(bool enabled) {
@@ skipping 453 matching lines @@
   if (parent)
     clip_parent = static_cast<WebLayerImpl*>(parent)->layer();
   layer_->SetClipParent(clip_parent);
 }
 
 Layer* WebLayerImpl::layer() const {
   return layer_.get();
 }
 
 }  // namespace cc_blink