Add V8 heap statistics in a time-line manner in tracing.

content/renderer/render_thread_impl.h

Index: content/renderer/render_thread_impl.h
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index 5a679b764d4dbc302ddb8c719df8d766b26ba46b..1ae72234a7d394501a82b70396892e73cf02123f 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -98,6 +98,7 @@ class PeerConnectionTracker;
 class RendererDemuxerAndroid;
 class RendererWebKitPlatformSupportImpl;
 class RenderProcessObserver;
+class V8HeapStatisticsMonitor;
 class VideoCaptureImplManager;
 class WebGraphicsContext3DCommandBufferImpl;
 class WebRTCIdentityService;
@@ -199,6 +200,10 @@ class CONTENT_EXPORT RenderThreadImpl : public RenderThread,
     return webkit_platform_support_.get();
   }
 
+  V8HeapStatisticsMonitor* v8_heap_statistics_monitor() {
+    return v8_heap_statistics_monitor_.get();
+  }
+
   IPC::ForwardingMessageFilter* compositor_output_surface_filter() const {
     return compositor_output_surface_filter_.get();
   }
@@ -518,6 +523,8 @@ class CONTENT_EXPORT RenderThreadImpl : public RenderThread,
   // The following flag is used to control layout test specific behavior.
   bool layout_test_mode_;
 
+  scoped_ptr<V8HeapStatisticsMonitor> v8_heap_statistics_monitor_;
+
   // Timer that periodically calls IdleHandler.
   base::RepeatingTimer<RenderThreadImpl> idle_timer_;