cc: add PaintTimeCounter to keep track of per frame paint time

cc/paint_time_counter.h

Index: cc/paint_time_counter.h
diff --git a/cc/paint_time_counter.h b/cc/paint_time_counter.h
new file mode 100644
index 0000000000000000000000000000000000000000..171f6dd8748ca82cdee4596a6302da0fb7abe5c0
--- /dev/null
+++ b/cc/paint_time_counter.h
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+// Copyright 2013 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_PAINT_TIME_COUNTER_H_
+#define CC_PAINT_TIME_COUNTER_H_
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time.h"
+#include "cc/ring_buffer.h"
+
+namespace cc {
+
+// Maintains a history of paint times for each frame
+class PaintTimeCounter {
+ public:
+  static scoped_ptr<PaintTimeCounter> create();
+
+  size_t HistorySize() const { return ring_buffer_.BufferSize(); }
+
+  // n = 0 returns the oldest and
+  // n = PaintTimeHistorySize() - 1 the most recent paint time.
+  base::TimeDelta GetPaintTimeOfRecentFrame(const size_t& n) const;
+
+  void SavePaintTime(const base::TimeDelta& total_paint_time);
+  void GetMinAndMaxPaintTime(base::TimeDelta* min, base::TimeDelta* max) const;
+
+ private:
+  PaintTimeCounter();
+
+  RingBuffer<base::TimeDelta, 80> ring_buffer_;
+  base::TimeDelta last_total_paint_time_;
+
+  DISALLOW_COPY_AND_ASSIGN(PaintTimeCounter);
+};
+
+}  // namespace cc
+
+#endif  // CC_PAINT_TIME_COUNTER_H_