CC Animations: Redirect all compositor animation requests to AnimationHost.

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 3c688a6bbd41ecde8d412817f8177df7ebe0a7a7..e28918235fe85eb8016cf51e07abfb46e07ded87 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;
 }