cc : Compute subtree has copy requests before property tree building

cc/trees/draw_property_utils.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 "cc/trees/draw_property_utils.h"
 
 #include <stddef.h>
 
 #include <vector>
 
@@ skipping 440 matching lines @@
 
 template <typename LayerType>
 static inline bool LayerShouldBeSkippedInternal(
     LayerType* layer,
     const TransformTree& transform_tree,
     const EffectTree& effect_tree) {
   const TransformNode* transform_node =
       transform_tree.Node(layer->transform_tree_index());
   const EffectNode* effect_node = effect_tree.Node(layer->effect_tree_index());
 
-  if (effect_node->has_render_surface &&
-      effect_node->num_copy_requests_in_subtree > 0)
+  if (effect_node->has_render_surface && effect_node->subtree_has_copy_request)

[weiliangc, 2017/04/19 17:58:48]

If subtree_has_copy_request is only useful here, why not just update the value
right before calling LayerShouldBeSkipped in FindLayersThatNeedUpdates? That way
we don't need to care about keep track of it during property tree builder?

[jaydasika, 2017/04/19 18:15:14]

I want to stop creating effect nodes for handling SetHideLayerAndSubtree
(https://bugs.chromium.org/p/chromium/issues/detail?id=595843#c5). To do that,
we will need to know subtree_has_copy_request during property tree building as
we have to create effects nodes in case copy requests exist. So, this CL is to
make that possible.

[weiliangc, 2017/04/19 21:21:54]

If we want to avoid sending those layers over, could we ignore them while
building layer list/property trees? and is it possible to not have
subtree_has_copy_request value in the node in the future?

[jaydasika, 2017/04/19 21:31:36]

Yes, that's the plan I have in mind : skip these layers while property tree
building and don't send them at commit so LayerImpl::layer_list won't have them.
I think it should be possible to delete effect node's subtree_has_copy_request.

     return false;
   // If the layer transform is not invertible, it should be skipped.
   // TODO(ajuma): Correctly process subtrees with singular transform for the
   // case where we may animate to a non-singular transform and wish to
   // pre-raster.
   return !transform_node->node_and_ancestors_are_animated_or_invertible ||
          effect_node->hidden_by_backface_visibility || !effect_node->is_drawn;
 }
 
 template <typename LayerType>
@@ skipping 616 matching lines @@
 void UpdateElasticOverscroll(PropertyTrees* property_trees,
                              const Layer* overscroll_elasticity_layer,
                              const gfx::Vector2dF& elastic_overscroll) {
   UpdateElasticOverscrollInternal(property_trees, overscroll_elasticity_layer,
                                   elastic_overscroll);
 }
 
 }  // namespace draw_property_utils
 
 }  // namespace cc