cc: Move render surface ownership from layers to the effect tree

cc/trees/damage_tracker.cc

Index: cc/trees/damage_tracker.cc
diff --git a/cc/trees/damage_tracker.cc b/cc/trees/damage_tracker.cc
index 5db534a713f50c9cc12c1ff17134f53b518cba7a..0910b43115311abf6868837234ed776c24959568 100644
--- a/cc/trees/damage_tracker.cc
+++ b/cc/trees/damage_tracker.cc
@@ -192,8 +192,9 @@ DamageTracker::DamageAccumulator DamageTracker::TrackDamageFromActiveLayers(
     if (layer == layer->layer_tree_impl()->hud_layer())
       continue;
 
-    if (layer->render_surface() && layer->render_surface() != target_surface)
-      ExtendDamageForRenderSurface(layer->render_surface(), &damage);
+    RenderSurfaceImpl* render_surface = layer->render_surface();
+    if (render_surface && render_surface != target_surface)
+      ExtendDamageForRenderSurface(render_surface, &damage);
     else
       ExtendDamageForLayer(layer, &damage);
   }