cc : Move screen space scale factor to root transform node

cc/trees/layer_tree_host_common.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_host_common.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 562 matching lines @@
       // update property trees before using them.
       draw_property_utils::UpdatePageScaleFactor(
           inputs->property_trees, inputs->page_scale_layer,
           inputs->page_scale_factor, inputs->device_scale_factor,
           inputs->device_transform);
       draw_property_utils::UpdateElasticOverscroll(
           inputs->property_trees, inputs->elastic_overscroll_application_layer,
           inputs->elastic_overscroll);
       // Similarly, the device viewport and device transform are shared
       // by both trees.
-      inputs->property_trees->clip_tree.SetViewportClip(
+      PropertyTrees* property_trees = inputs->property_trees;
+      property_trees->clip_tree.SetViewportClip(
           gfx::RectF(gfx::SizeF(inputs->device_viewport_size)));
-      inputs->property_trees->transform_tree.SetDeviceTransform(
+      float page_scale_factor_for_root =
+          inputs->page_scale_layer == inputs->root_layer
+              ? inputs->page_scale_factor
+              : 1.f;
+      property_trees->transform_tree.SetScreenSpaceScale(
+          inputs->device_scale_factor, page_scale_factor_for_root,
+          inputs->device_transform);
+      property_trees->transform_tree.SetDeviceTransform(
           inputs->device_transform, inputs->root_layer->position());
-      inputs->property_trees->transform_tree.SetDeviceTransformScaleFactor(
+      property_trees->transform_tree.SetDeviceTransformScaleFactor(
           inputs->device_transform);
       draw_property_utils::ComputeVisibleRects(
           inputs->root_layer, inputs->property_trees,
           inputs->can_render_to_separate_surface, &visible_layer_list);
       break;
     }
   }
 
   if (should_measure_property_tree_performance) {
     TRACE_EVENT_BEGIN0(TRACE_DISABLED_BY_DEFAULT("cc.debug.cdp-perf"),
@@ skipping 109 matching lines @@
 
 PropertyTrees* GetPropertyTrees(Layer* layer) {
   return layer->GetLayerTree()->property_trees();
 }
 
 PropertyTrees* GetPropertyTrees(LayerImpl* layer) {
   return layer->layer_tree_impl()->property_trees();
 }
 
 }  // namespace cc