Update from https://crrev.com/320343

cc/trees/occlusion_tracker.cc

 // Copyright 2012 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 "cc/trees/occlusion_tracker.h"
 
 #include <algorithm>
 
 #include "cc/base/math_util.h"
 #include "cc/base/region.h"
@@ skipping 137 matching lines @@
   return !rs->screen_space_transforms_are_animating();
 }
 static inline bool SurfaceTransformsToScreenKnown(const RenderSurfaceImpl* rs) {
   return true;
 }
 
 static inline bool LayerIsInUnsorted3dRenderingContext(const Layer* layer) {
   return layer->Is3dSorted();
 }
 static inline bool LayerIsInUnsorted3dRenderingContext(const LayerImpl* layer) {
-  return false;
+  return layer->Is3dSorted();
 }
 
 template <typename LayerType>
 static inline bool LayerIsHidden(const LayerType* layer) {
   return layer->hide_layer_and_subtree() ||
          (layer->parent() && LayerIsHidden(layer->parent()));
 }
 
 template <typename LayerType>
 void OcclusionTracker<LayerType>::EnterRenderTarget(
@@ skipping 308 matching lines @@
   for (size_t i = 0; i < occluded.GetRegionComplexity(); ++i)
     visible_region.Subtract(occluded.GetRect(i));
   return visible_region;
 }
 
 // Instantiate (and export) templates here for the linker.
 template class OcclusionTracker<Layer>;
 template class OcclusionTracker<LayerImpl>;
 
 }  // namespace cc