Update from chromium https://crrev.com/301725/

base/profiler/scoped_tracker.h

+// Copyright 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 BASE_PROFILER_SCOPED_TRACKER_H_
+#define BASE_PROFILER_SCOPED_TRACKER_H_
+
+//------------------------------------------------------------------------------
+// Utilities for temporarily instrumenting code to dig into issues that were
+// found using profiler data.
+
+#include "base/base_export.h"
+#include "base/location.h"
+#include "base/profiler/scoped_profile.h"
+
+namespace tracked_objects {
+
+// ScopedTracker instruments a region within the code if the instrumentation is
+// enabled. It can be used, for example, to find out if a source of jankiness is
+// inside the instrumented code region.
+class BASE_EXPORT ScopedTracker {
+ public:
+  ScopedTracker(const Location& location);
+
+  // Enables instrumentation for the remainder of the current process' life. If
+  // this function is not called, all profiler instrumentations are no-ops.
+  static void Enable();
+
+ private:
+  const ScopedProfile scoped_profile_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedTracker);
+};
+
+}  // namespace tracked_objects
+
+#endif  // BASE_PROFILER_SCOPED_TRACKER_H_