cc: Reduce surface contents scale adjustments.

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 823 matching lines @@
           .is_showing_backface;
 }
 
 void EffectTree::UpdateSurfaceContentsScale(EffectNode* effect_node) {
   if (!effect_node->has_render_surface) {
     effect_node->surface_contents_scale = gfx::Vector2dF(1.0f, 1.0f);
     return;
   }
 
   TransformTree& transform_tree = property_trees()->transform_tree;
+  TransformNode* transform_node =
+      transform_tree.Node(effect_node->transform_id);
+  if (transform_node->is_currently_animating) {

[ajuma, 2017/04/04 21:41:11]

Would it make sense to tie this to
LayerTreeSettings::layer_transforms_should_scale_layer_contents == false instead
of to whether we're animating?

[reveman, 2017/04/05 13:20:15]

Makes sense. Done.

+    effect_node->surface_contents_scale = gfx::Vector2dF(1.0f, 1.0f);

[ajuma, 2017/04/04 21:41:11]

Is device scale factor a better choice than 1 here? (to match the ideal contents
scale of layers)

[reveman, 2017/04/05 13:20:15]

Yes, it is. Done.

+    return;
+  }
   float layer_scale_factor = transform_tree.device_scale_factor() *
                              transform_tree.device_transform_scale_factor();
-  TransformNode* transform_node =
-      transform_tree.Node(effect_node->transform_id);
   if (transform_node->in_subtree_of_page_scale_layer)
     layer_scale_factor *= transform_tree.page_scale_factor();
   effect_node->surface_contents_scale =
       MathUtil::ComputeTransform2dScaleComponents(
           transform_tree.ToScreen(transform_node->id), layer_scale_factor);
 }
 
 EffectNode* EffectTree::FindNodeFromElementId(ElementId id) {
   auto iterator = property_trees()->element_id_to_effect_node_index.find(id);
   if (iterator == property_trees()->element_id_to_effect_node_index.end())
@@ skipping 1253 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