Mozart: Directly associate the renderer with the view tree.

services/gfx/compositor/renderer_impl.cc

Index: services/gfx/compositor/renderer_impl.cc
diff --git a/services/gfx/compositor/renderer_impl.cc b/services/gfx/compositor/renderer_impl.cc
index 7c730b0c1fe079477905deebad95bd6fb0dee8fe..d01454a4f76a9ca060cf677eae88582f64734c63 100644
--- a/services/gfx/compositor/renderer_impl.cc
+++ b/services/gfx/compositor/renderer_impl.cc
@@ -33,6 +33,10 @@ void RendererImpl::SetRootScene(
                         viewport.Pass());
 }
 
+void RendererImpl::ResetRootScene() {
+  engine_->ResetRootScene(state_);
+}
+
 void RendererImpl::HitTest(mojo::PointPtr point,
                            const HitTestCallback& callback) {
   engine_->HitTest(state_, point.Pass(), callback);