Track transform animation content readiness on TransformNode.

cc/trees/transform_node.cc

Index: cc/trees/transform_node.cc
diff --git a/cc/trees/transform_node.cc b/cc/trees/transform_node.cc
index 6f89261dd29566625679abe5b7a04b475ee27d92..b9d75c26f2e5eac2e5b4a4d2da099ee93b54ed16 100644
--- a/cc/trees/transform_node.cc
+++ b/cc/trees/transform_node.cc
@@ -37,6 +37,7 @@ TransformNode::TransformNode()
       moved_by_outer_viewport_bounds_delta_y(false),
       in_subtree_of_page_scale_layer(false),
       transform_changed(false),
+      ready_since_animation(true),
       post_local_scale_factor(1.0f) {}
 
 TransformNode::TransformNode(const TransformNode&) = default;