Track transform animation content readiness on TransformNode.

cc/trees/property_tree.cc

Index: cc/trees/property_tree.cc
diff --git a/cc/trees/property_tree.cc b/cc/trees/property_tree.cc
index f450baa7067a5b3aa83fa9b6f08a201f17eb2e24..21bf595a623927ac205e1b74b465396996678fae 100644
--- a/cc/trees/property_tree.cc
+++ b/cc/trees/property_tree.cc
@@ -193,6 +193,7 @@ bool TransformTree::OnTransformAnimated(ElementId element_id,
   node->local = transform;
   node->needs_local_transform_update = true;
   node->transform_changed = true;
+  node->ready_since_animation = false;

[wkorman, 2017/05/20 01:31:27]

Is it ok that we do this on both main and impl threads? I think it will be
ignored on main thread since only LayerTreeHostImpl actually reads the value.

   property_trees()->changed = true;
   set_needs_update(true);
   return true;