CC Animations: Establish AnimationHost, AnimationTimeline and AnimationPlayer

cc/layers/layer.cc

Index: cc/layers/layer.cc
diff --git a/cc/layers/layer.cc b/cc/layers/layer.cc
index 4d03f565efefc9ba936722715815d3f6f67e4bbd..fc7d0da5fb76fe249c2993df59b9c75885e041d3 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -117,10 +117,13 @@ void Layer::SetLayerTreeHost(LayerTreeHost* host) {
   if (layer_tree_host_ == host)
     return;
 
-  if (layer_tree_host_)
+  if (layer_tree_host_) {
     layer_tree_host_->property_trees()->needs_rebuild = true;
-
+    layer_tree_host_->UnregisterLayer(this);
+  }
   layer_tree_host_ = host;
+  if (layer_tree_host_)
+    layer_tree_host_->RegisterLayer(this);
 
   // When changing hosts, the layer needs to commit its properties to the impl
   // side for the new host.