Mozart: Directly associate the renderer with the view tree.

services/gfx/compositor/renderer_state.h

Index: services/gfx/compositor/renderer_state.h
diff --git a/services/gfx/compositor/renderer_state.h b/services/gfx/compositor/renderer_state.h
index 54e688bcbc058988ecbe408a3c415e6206d9123a..d0ca990d6455876bb37e4a4e57114f09434f57f1 100644
--- a/services/gfx/compositor/renderer_state.h
+++ b/services/gfx/compositor/renderer_state.h
@@ -53,6 +53,10 @@ class RendererState {
                     uint32_t version,
                     const mojo::Rect& viewport);
 
+  // Resets the root scene and clears the current frame and cached dependencies.
+  // If different, invalidates the snapshot and returns true.
+  bool ResetRootScene();
+
   // The currently composited frame, may be null if none.
   const std::shared_ptr<RenderFrame>& frame() { return frame_; }