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

content/public/renderer/v8_heap_statistics_collector.h

Index: content/public/renderer/v8_heap_statistics_collector.h
diff --git a/content/public/renderer/v8_heap_statistics_collector.h b/content/public/renderer/v8_heap_statistics_collector.h
new file mode 100644
index 0000000000000000000000000000000000000000..2934018c489d085b87acccf02949118a5814efb1
--- /dev/null
+++ b/content/public/renderer/v8_heap_statistics_collector.h
@@ -0,0 +1,40 @@
+// Copyright (c) 2014 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 CONTENT_PUBLIC_RENDERER_V8_HEAP_STATISTICS_COLLECTOR_H_
+#define CONTENT_PUBLIC_RENDERER_V8_HEAP_STATISTICS_COLLECTOR_H_
+
+#include "base/callback.h"
+#include "content/common/content_export.h"
+
+namespace base {
+class Value;
+}
+
+namespace content {
+
+// Retrieves statistics about v8, asynchronously.
+class CONTENT_EXPORT V8HeapStatisticsCollector {
+ public:
+  static V8HeapStatisticsCollector* Instance();
+  virtual ~V8HeapStatisticsCollector() {}
+
+  struct Statistics {
+    Statistics() : total_bytes(0), used_bytes(0) {}
+    size_t total_bytes;
+    size_t used_bytes;
+  };
+  typedef base::Callback<void(const Statistics&)> ResultCallback;
+
+  // Begins collecting heap statistics. Only one collection can be pending at
+  // once. Returns true on success. Callback will not be called if initiation
+  // fails.
+  //
+  // Must be called on the RenderThread.
+  virtual bool InitiateCollection(const ResultCallback& callback) = 0;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_RENDERER_V8_HEAP_STATISTICS_COLLECTOR_H_