Replace LayerImpl::sorting_context_id with transform reference.

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 1869 matching lines @@
       hit =
           PointHitsLayer(layer, screen_space_point, &distance_to_intersection);
     else
       hit = PointHitsLayer(layer, screen_space_point, nullptr);
 
     if (!hit)
       continue;
 
     bool in_front_of_previous_candidate =
         state->closest_match &&
-        layer->sorting_context_id() ==
-            state->closest_match->sorting_context_id() &&
+        layer->GetSortingContextId() ==
+            state->closest_match->GetSortingContextId() &&
         distance_to_intersection >
             state->closest_distance + std::numeric_limits<float>::epsilon();
 
     if (!state->closest_match || in_front_of_previous_candidate) {
       state->closest_distance = distance_to_intersection;
       state->closest_match = layer;
     }
   }
 }
 
@@ skipping 182 matching lines @@
 
 void LayerTreeImpl::ResetAllChangeTracking() {
   layers_that_should_push_properties_.clear();
   // Iterate over all layers, including masks.
   for (auto& layer : *layers_)
     layer->ResetChangeTracking();
   property_trees_.ResetAllChangeTracking();
 }
 
 }  // namespace cc