[cc] Rename all cc/ filenames to Chromium style

cc/frame_rate_counter.h

 // Copyright 2012 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 CCFrameRateCounter_h
+#define CCFrameRateCounter_h
+
+#if USE(ACCELERATED_COMPOSITING)
+
+#include "base/basictypes.h"
+#include <wtf/PassOwnPtr.h>
+
+namespace cc {
+
+// This class maintains a history of timestamps, and provides functionality to
+// intelligently compute average frames per second (and standard deviation).
+class CCFrameRateCounter {
+public:
+    static PassOwnPtr<CCFrameRateCounter> create()
+    {
+        return adoptPtr(new CCFrameRateCounter());
+    }
+
+    void markBeginningOfFrame(double timestamp);
+    void markEndOfFrame();
+    int currentFrameNumber() const { return m_currentFrameNumber; }
+    void getAverageFPSAndStandardDeviation(double& averageFPS, double& standardDeviation) const;
+    int timeStampHistorySize() const { return kTimeStampHistorySize; }
+
+    // n = 0 returns the oldest frame retained in the history,
+    // while n = timeStampHistorySize() - 1 returns the timestamp most recent frame.
+    double timeStampOfRecentFrame(int /* n */);
+
+    // This is a heuristic that can be used to ignore frames in a reasonable way. Returns
+    // true if the given frame interval is too fast or too slow, based on constant thresholds.
+    bool isBadFrameInterval(double intervalBetweenConsecutiveFrames) const;
+
+    int droppedFrameCount() const { return m_droppedFrameCount; }
+
+private:
+    CCFrameRateCounter();
+
+    double frameInterval(int frameNumber) const;
+    int frameIndex(int frameNumber) const;
+    bool isBadFrame(int frameNumber) const;
+
+    // Two thresholds (measured in seconds) that describe what is considered to be a "no-op frame" that should not be counted.
+    // - if the frame is too fast, then given our compositor implementation, the frame probably was a no-op and did not draw.
+    // - if the frame is too slow, then there is probably not animating content, so we should not pollute the average.
+    static const double kFrameTooFast;
+    static const double kFrameTooSlow;
+
+    // If a frame takes longer than this threshold (measured in seconds) then we
+    // (naively) assume that it missed a screen refresh; that is, we dropped a frame.
+    // FIXME: Determine this threshold based on monitor refresh rate, crbug.com/138642.
+    static const double kDroppedFrameTime;
+
+    static const int kTimeStampHistorySize = 120;
+
+    int m_currentFrameNumber;
+    double m_timeStampHistory[kTimeStampHistorySize];
+
+    int m_droppedFrameCount;
+
+    DISALLOW_COPY_AND_ASSIGN(CCFrameRateCounter);
+};
+
+} // namespace cc
+
+#endif // USE(ACCELERATED_COMPOSITING)
+
+#endif