CC Animations: Make LayerAnimationController creation optional

cc/blink/web_layer_impl.cc

Index: cc/blink/web_layer_impl.cc
diff --git a/cc/blink/web_layer_impl.cc b/cc/blink/web_layer_impl.cc
index 8bad92a002e6b9bd13d3aca21f2b800da2ddeded..dd836d1c6cba4aaae946105b759a76830be98da8 100644
--- a/cc/blink/web_layer_impl.cc
+++ b/cc/blink/web_layer_impl.cc
@@ -62,7 +62,8 @@ WebLayerImpl::WebLayerImpl(scoped_refptr<Layer> layer) : layer_(layer) {
 
 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;
 }