cc : Make CallFunctionForSubtree on impl use layer iterator

cc/trees/layer_tree_host_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_host_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 1607 matching lines @@
         active_tree_->root_layer(),
         active_tree_->hud_layer(),
         *frame->render_surface_layer_list,
         debug_state_);
   }
 
   bool is_new_trace;
   TRACE_EVENT_IS_NEW_TRACE(&is_new_trace);
   if (is_new_trace) {
     if (pending_tree_) {
-      LayerTreeHostCommon::CallFunctionForSubtree(
-          pending_tree_->root_layer(),
-          [](LayerImpl* layer) { layer->DidBeginTracing(); });
+      LayerTreeHostCommon::CallFunctionForEveryLayer(
+          pending_tree(), [](LayerImpl* layer) { layer->DidBeginTracing(); });
     }
-    LayerTreeHostCommon::CallFunctionForSubtree(
-        active_tree_->root_layer(),
-        [](LayerImpl* layer) { layer->DidBeginTracing(); });
+    LayerTreeHostCommon::CallFunctionForEveryLayer(
+        active_tree(), [](LayerImpl* layer) { layer->DidBeginTracing(); });
   }
 
   {
     TRACE_EVENT0("cc", "DrawLayers.FrameViewerTracing");
     TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(
         frame_viewer_instrumentation::kCategoryLayerTree,
         "cc::LayerTreeHostImpl", id_, AsValueWithFrame(frame));
   }
 
   const DrawMode draw_mode = GetDrawMode();
@@ skipping 2278 matching lines @@
   return task_runner_provider_->HasImplThread();
 }
 
 bool LayerTreeHostImpl::CommitToActiveTree() const {
   // In single threaded mode we skip the pending tree and commit directly to the
   // active tree.
   return !task_runner_provider_->HasImplThread();
 }
 
 }  // namespace cc