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..6c5829bd83ed85899c5327934d229c33bb0b902d
--- /dev/null
+++ b/cc/paint_time_counter.h
@@ -0,0 +1,39 @@
+// 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 "cc/ring_buffer.h"
+
+namespace cc {
+
+// Maintains a history of paint times for each frame in milliseconds
+class PaintTimeCounter {
+ public:
+  static scoped_ptr<PaintTimeCounter> create();
+
+	size_t HistorySize() const { return ring_buffer_.BufferSize(); }

[reveman, 2013/01/11 16:10:49]

nit: fix indent

+
+  // n = 0 returns the oldest and
+  // n = PaintTimeHistorySize() - 1 the most recent paint time.
+	double GetPaintTimeOfRecentFrame(int n) const;

[reveman, 2013/01/11 16:10:49]

also here

+
+  void SavePaintTime(double total_paint_time);
+  void GetMinAndMaxPaintTime(double& min, double& max) const;
+
+ private:
+	PaintTimeCounter();

[reveman, 2013/01/11 16:10:49]

and here

+
+	RingBuffer<double, 80> ring_buffer_;

[reveman, 2013/01/11 16:10:49]

here

+  double last_paint_time_;
+
+  DISALLOW_COPY_AND_ASSIGN(PaintTimeCounter);
+};
+
+}  // namespace cc
+
+#endif  // CC_PAINT_TIME_COUNTER_H_