Mozart: Improve internal scene graph representation.

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [DartPackage="mojo_services"]
 module mojo.gfx.composition;
 
 import "mojo/services/gfx/composition/interfaces/nodes.mojom";
 import "mojo/services/gfx/composition/interfaces/resources.mojom";
 import "mojo/services/gfx/composition/interfaces/scene_token.mojom";
@@ skipping 133 matching lines @@
   // All pending incremental updates are applied atomically when the scene
   // is published and the new state is labeled with the version indicated
   // in the associated metadata.
   //
   // The |metadata| describes how the published scene should be presented.
   // If null, this method behaves as if a |SceneMetadata| object initialized
   // with default values had been supplied.
   //
   // 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.
   GetScheduler(SceneScheduler& scheduler);
 };
 
 // An interface applications may implement to receive events from a scene.
 interface SceneListener {
   // Called when a resource has become unavailable.
   //
@@ skipping 49 matching lines @@
   // scene are to be shown on the display output assuming everything is
   // fully rendered and submitted by the appropriate deadline.
   //
   // Expressed in microseconds in the |MojoTimeTicks| timebase.
   //
   // A value of 0 means "as soon as possible".
   //
   // See also: |FrameInfo.presentation_time|.
   int64 presentation_time = 0;
 };