Add TRACE_EVENT_IS_NEW_TRACE as a way to snapshot objects at start of recording

cc/layers/layer_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/layers/layer_impl.h"
 
 #include "base/debug/trace_event.h"
 #include "base/stringprintf.h"
 #include "cc/animation/animation_registrar.h"
 #include "cc/animation/scrollbar_animation_controller.h"
@@ skipping 925 matching lines @@
   double_sided_ = double_sided;
   NoteLayerPropertyChangedForSubtree();
 }
 
 Region LayerImpl::VisibleContentOpaqueRegion() const {
   if (contents_opaque())
     return visible_content_rect();
   return Region();
 }
 
+void LayerImpl::DidBeginTracing() {}
+
 void LayerImpl::DidLoseOutputSurface() {}
 
 void LayerImpl::SetMaxScrollOffset(gfx::Vector2d max_scroll_offset) {
   if (max_scroll_offset_ == max_scroll_offset)
     return;
   max_scroll_offset_ = max_scroll_offset;
 
   layer_tree_impl()->set_needs_update_draw_properties();
   UpdateScrollbarPositions();
 }
@@ skipping 191 matching lines @@
 
 size_t LayerImpl::GPUMemoryUsageInBytes() const { return 0; }
 
 scoped_ptr<base::Value> LayerImpl::AsValue() const {
   scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
   AsValueInto(state.get());
   return state.PassAs<base::Value>();
 }
 
 }  // namespace cc