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

cc/layers/layer_impl.h

 // 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.
 
 #ifndef CC_LAYERS_LAYER_IMPL_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <string>
 
 #include "base/logging.h"
@@ skipping 366 matching lines @@
   virtual bool LayerIsAlwaysDamaged() const;
 
   LayerAnimationController* layer_animation_controller() {
     return layer_animation_controller_.get();
   }
 
   virtual Region VisibleContentOpaqueRegion() const;
 
   virtual void DidBecomeActive();
 
+  virtual void DidBeginTracing();
+
   // Indicates that the surface previously used to render this layer
   // was lost and that a new one has been created. Won't be called
   // until the new surface has been created successfully.
   virtual void DidLoseOutputSurface();
 
   ScrollbarAnimationController* scrollbar_animation_controller() const {
     return scrollbar_animation_controller_.get();
   }
 
   void SetScrollbarOpacity(float opacity);
@@ skipping 158 matching lines @@
   // Group of properties that need to be computed based on the layer tree
   // hierarchy before layers can be drawn.
   DrawProperties<LayerImpl, RenderSurfaceImpl> draw_properties_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_