Mozart: Improve internal scene graph representation.

services/gfx/compositor/graph/resource_def.cc

Index: services/gfx/compositor/graph/resource_def.cc
diff --git a/services/gfx/compositor/graph/resource_def.cc b/services/gfx/compositor/graph/resource_def.cc
index f837f1e84312621da55ec525a15c07087f2d6731..2ebf95703c8c7285069f8e870408533f6dad5e92 100644
--- a/services/gfx/compositor/graph/resource_def.cc
+++ b/services/gfx/compositor/graph/resource_def.cc
@@ -8,11 +8,21 @@
 
 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;
 }