Mozart: Improve internal scene graph representation.

mojo/services/gfx/composition/interfaces/scenes.mojom

Index: mojo/services/gfx/composition/interfaces/scenes.mojom
diff --git a/mojo/services/gfx/composition/interfaces/scenes.mojom b/mojo/services/gfx/composition/interfaces/scenes.mojom
index d9c5c69a103fead66d8c97564f11dc59713e1fb9..2e7f631033aae59e0319720459ff326e3f795fe1 100644
--- a/mojo/services/gfx/composition/interfaces/scenes.mojom
+++ b/mojo/services/gfx/composition/interfaces/scenes.mojom
@@ -151,8 +151,8 @@ interface Scene {
   //
   // Publishing a scene graph applies all pending updates.  It is an error
   // to publish updates which cause the scene state to become inconsistent,
-  // such as by having nodes which refer to non-existent resources; the
-  // connection will be closed.
+  // such as by having nodes which refer to non-existent resources or
+  // introducing cycles in the scene's nodes; the connection will be closed.
   Publish(SceneMetadata? metadata);
 
   // Gets a scheduler for scheduling upcoming scene operations.