cc : Fix occlusion tracking bug for contributing surface

cc/trees/layer_tree_impl.cc

 // Copyright 2011 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/layer_tree_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 940 matching lines @@
         Occlusion occlusion =
             inside_replica ? Occlusion()
                            : occlusion_tracker.GetCurrentOcclusionForLayer(
                                  it->DrawTransform());
         it->draw_properties().occlusion_in_content_space = occlusion;
       }
 
       if (it.represents_contributing_render_surface()) {
         // Surfaces aren't used by the tile raster code, so they can have
         // occlusion regardless of replicas.
+        const RenderSurfaceImpl* occlusion_surface =
+            occlusion_tracker.OcclusionSurfaceForContributingSurface();
+        gfx::Transform draw_transform;
+        if (occlusion_surface) {
+          // We are calculating transform between two render surfaces. So, we

[enne (OOO), 2016/07/14 19:51:41]

I think Apply and Remove look too similar but do very different things, re:
pre-concat vs post-concat.  I think you should either not make them functions
and do that work inline here or add some additional words to the function names
ApplySublayerScaleAtTarget or some such that make it clear that they are not
inverses of each other.

[jaydasika, 2016/07/14 21:00:46]

I have renamed them to PostConcatSublayerScale and ConcatInverseSublayerScale.
In a follow-up, I will make all callers of PostConcat send the target effect
node id to it directly. So these functions will just grab the sublayer scale
from the effect node they are send and concat/postConcat to the transform. 

+          // need to apply the sublayer scale at target and remove the sublayer
+          // scale at source.
+          property_trees()->transform_tree.ComputeTransform(
+              it->render_surface()->TransformTreeIndex(),
+              occlusion_surface->TransformTreeIndex(), &draw_transform);
+          // We don't have to apply sublayer scale when target is root.
+          if (occlusion_surface->TransformTreeIndex() != 0)
+            draw_property_utils::ApplySublayerScale(
+                occlusion_surface->EffectTreeIndex(),
+                property_trees()->effect_tree, &draw_transform);
+          draw_property_utils::RemoveSublayerScale(
+              it->render_surface()->EffectTreeIndex(),
+              property_trees()->effect_tree, &draw_transform);
+        }
+
         Occlusion occlusion =
             occlusion_tracker.GetCurrentOcclusionForContributingSurface(
-                it->render_surface()->draw_transform());
+                draw_transform);
         it->render_surface()->set_occlusion_in_content_space(occlusion);
         // Masks are used to draw the contributing surface, so should have
         // the same occlusion as the surface (nothing inside the surface
         // occludes them).
         if (LayerImpl* mask = it->render_surface()->MaskLayer()) {
           Occlusion mask_occlusion =
               inside_replica
                   ? Occlusion()
                   : occlusion_tracker.GetCurrentOcclusionForContributingSurface(
                         it->render_surface()->draw_transform() *
@@ skipping 1018 matching lines @@
 
 void LayerTreeImpl::ResetAllChangeTracking() {
   layers_that_should_push_properties_.clear();
   // Iterate over all layers, including masks and replicas.
   for (auto& layer : *layers_)
     layer->ResetChangeTracking();
   property_trees_.ResetAllChangeTracking();
 }
 
 }  // namespace cc