cc : Don't draw animating layers which are transparent but raster them.

cc/trees/property_tree.cc

 // Copyright 2014 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 <stddef.h>
 
 #include <set>
 #include <vector>
 
 #include "base/logging.h"
@@ skipping 779 matching lines @@
   if (parent_node)
     node->screen_space_opacity *= parent_node->screen_space_opacity;
 }
 
 void EffectTree::UpdateIsDrawn(EffectNode* node, EffectNode* parent_node) {
   // Nodes that have screen space opacity 0 are hidden. So they are not drawn.
   // Exceptions:
   // 1) Nodes that contribute to copy requests, whether hidden or not, must be
   //    drawn.
   // 2) Nodes that have a background filter.
   // 3) Nodes with animating screen space opacity on main thread or pending tree

[weiliangc, 2017/05/03 21:19:50]

Update the comment?

   //    are drawn if their parent is drawn irrespective of their opacity.
   if (node->has_copy_request)
     node->is_drawn = true;
   else if (EffectiveOpacity(node) == 0.f &&
-           (!node->has_potential_opacity_animation ||
-            property_trees()->is_active) &&
+           !node->has_potential_opacity_animation &&
            node->background_filters.IsEmpty())
     node->is_drawn = false;
   else if (parent_node)
     node->is_drawn = parent_node->is_drawn;
   else
     node->is_drawn = true;
 }
 
 void EffectTree::UpdateEffectChanged(EffectNode* node,
                                      EffectNode* parent_node) {
@@ skipping 1325 matching lines @@
   const EffectNode* effect_node = effect_tree.Node(effect_id);
 
   if (effect_node->surface_contents_scale.x() != 0.0 &&
       effect_node->surface_contents_scale.y() != 0.0)
     screen_space_transform.Scale(1.0 / effect_node->surface_contents_scale.x(),
                                  1.0 / effect_node->surface_contents_scale.y());
   return screen_space_transform;
 }
 
 }  // namespace cc