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

cc/layers/picture_layer_impl.h

 // Copyright 2012 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_PICTURE_LAYER_IMPL_H_
 #define CC_LAYERS_PICTURE_LAYER_IMPL_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 23 matching lines @@
   // LayerImpl overrides.
   virtual const char* LayerTypeAsString() const OVERRIDE;
   virtual scoped_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl)
       OVERRIDE;
   virtual void PushPropertiesTo(LayerImpl* layer) OVERRIDE;
   virtual void AppendQuads(QuadSink* quad_sink,
                            AppendQuadsData* append_quads_data) OVERRIDE;
   virtual void DumpLayerProperties(std::string* str, int indent) const OVERRIDE;
   virtual void UpdateTilePriorities() OVERRIDE;
   virtual void DidBecomeActive() OVERRIDE;
+  virtual void DidBeginTracing() OVERRIDE;
   virtual void DidLoseOutputSurface() OVERRIDE;
   virtual void CalculateContentsScale(float ideal_contents_scale,
                                       float device_scale_factor,
                                       float page_scale_factor,
                                       bool animating_transform_to_screen,
                                       float* contents_scale_x,
                                       float* contents_scale_y,
                                       gfx::Size* content_bounds) OVERRIDE;
   virtual skia::RefPtr<SkPicture> GetPicture() OVERRIDE;
 
@@ skipping 72 matching lines @@
   bool raster_source_scale_was_animating_;
   bool is_using_lcd_text_;
 
   friend class PictureLayer;
   DISALLOW_COPY_AND_ASSIGN(PictureLayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_PICTURE_LAYER_IMPL_H_