Remove owning_id from EffectNode and replace it by an opaque stable_id

cc/trees/effect_node.h

Index: cc/trees/effect_node.h
diff --git a/cc/trees/effect_node.h b/cc/trees/effect_node.h
index 9d37b87f30ee52f898df2c82f686517eadae3daa..54dd3f07cbe78fb70441ed3cd05872b384c13707 100644
--- a/cc/trees/effect_node.h
+++ b/cc/trees/effect_node.h
@@ -27,8 +27,9 @@ struct CC_EXPORT EffectNode {
   int id;
   // The node index of the parent node in the effect tree node vector.
   int parent_id;
-  // The layer id of the layer that owns this node.
-  int owning_layer_id;
+
+  // An identifer for this effect that is generally stable across commits.
+  int stable_id;
 
   float opacity;
   float screen_space_opacity;
@@ -61,7 +62,9 @@ struct CC_EXPORT EffectNode {
   bool subtree_has_copy_request;
   int transform_id;
   int clip_id;
-  // Effect node id of which this effect contributes to.
+
+  // This is the id of the ancestor effect node that induces a
+  // RenderSurfaceImpl.
   int target_id;
   int mask_layer_id;
   int closest_ancestor_with_copy_request_id;