not for commit/review (thread cost tracker)

cc/debug/worker_thread_cost_tracker.h

Index: cc/debug/worker_thread_cost_tracker.h
diff --git a/cc/debug/worker_thread_cost_tracker.h b/cc/debug/worker_thread_cost_tracker.h
new file mode 100644
index 0000000000000000000000000000000000000000..b5686c95b4fc24f30fabb3bc0645c9c8f1d2b6da
--- /dev/null
+++ b/cc/debug/worker_thread_cost_tracker.h
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+// 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 CC_DEBUG_WORKER_THREAD_COST_TRACKER_H_
+#define CC_DEBUG_WORKER_THREAD_COST_TRACKER_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "base/time/time.h"
+
+namespace cc {
+
+class WorkerThreadCostTracker {
+ public:
+  class Probe {
+   public:
+    Probe(WorkerThreadCostTracker* tracker, int tracked_source_frame_number);
+    ~Probe();
+
+    void Start(int source_frame_number);
+    void Stop();
+
+   private:
+    WorkerThreadCostTracker* tracker_;
+    int tracked_source_frame_number_;
+    base::PlatformThreadId tracker_thread_id_;
+
+    bool started_;
+    base::TimeTicks start_;
+    base::TimeDelta cost_;
+
+    base::ThreadChecker thread_checker_;
+  };
+
+  WorkerThreadCostTracker();
+  ~WorkerThreadCostTracker();
+
+  void set_source_frame_to_track(int source_frame_number) {
+    source_frame_number_ = source_frame_number;
+  }
+  void reset_cost() { cost_ = base::TimeDelta(); }
+  base::TimeDelta get_cost() { return cost_; }
+
+  scoped_ptr<Probe> CreateProbe();
+
+ private:
+  friend class Probe;
+
+  void add_cost(const base::TimeDelta& cost) { cost_ += cost; }
+
+  int source_frame_number_;
+  base::TimeDelta cost_;
+};
+
+}  // namespace cc
+
+#endif  // CC_DEBUG_WORKER_THREAD_COST_TRACKER_H_