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

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index c7ea9c71e78c6fcd3727d6326465f816285e075e..7d667314b6d45a18a9549fab8c8d00272189ba77 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -24,6 +24,7 @@
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_tokenizer.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/thread_task_runner_handle.h"
 #include "base/threading/thread_local.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/values.h"
@@ -95,6 +96,7 @@
 #include "content/renderer/service_worker/embedded_worker_context_message_filter.h"
 #include "content/renderer/service_worker/embedded_worker_dispatcher.h"
 #include "content/renderer/shared_worker/embedded_shared_worker_stub.h"
+#include "content/renderer/v8_heap_statistics_monitor.h"
 #include "grit/content_resources.h"
 #include "ipc/ipc_channel_handle.h"
 #include "ipc/ipc_forwarding_message_filter.h"
@@ -360,6 +362,8 @@ void RenderThreadImpl::Init() {
   v8::V8::SetCounterFunction(base::StatsTable::FindLocation);
   v8::V8::SetCreateHistogramFunction(CreateHistogram);
   v8::V8::SetAddHistogramSampleFunction(AddHistogramSample);
+  v8_heap_statistics_monitor_.reset(
+      new V8HeapStatisticsMonitor(base::ThreadTaskRunnerHandle::Get()));
 
 #if defined(OS_MACOSX) || defined(OS_ANDROID)
   // On Mac and Android, the select popups are rendered by the browser.