Mozart: Improve internal scene graph representation.

services/gfx/compositor/graph/resource_def.cc

 // 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.
 
 #include "services/gfx/compositor/graph/resource_def.h"
 
 #include "base/logging.h"
 
 namespace compositor {
 
-SceneResourceDef::SceneResourceDef(SceneDef* referenced_scene)
-    : referenced_scene_(referenced_scene) {}
+ResourceDef::ResourceDef() {}
+
+ResourceDef::~ResourceDef() {}
+
+SceneResourceDef::SceneResourceDef(
+    const mojo::gfx::composition::SceneToken& scene_token,
+    const base::WeakPtr<SceneDef>& referenced_scene)
+    : scene_token_(scene_token), referenced_scene_(referenced_scene) {}
 
 SceneResourceDef::~SceneResourceDef() {}
 
+scoped_refptr<const SceneResourceDef> SceneResourceDef::Unlink() const {
+  return new SceneResourceDef(scene_token_, base::WeakPtr<SceneDef>());
+}
+
 ResourceDef::Type SceneResourceDef::type() const {
   return Type::kScene;
 }
 
 ImageResourceDef::ImageResourceDef(const std::shared_ptr<RenderImage>& image)
     : image_(image) {
   DCHECK(image);
 }
 
 ImageResourceDef::~ImageResourceDef() {}
 
 ResourceDef::Type ImageResourceDef::type() const {
   return Type::kImage;
 }
 
 }  // namespace compositor