[Cast] In Audio/VideoSender, drop frames when too-long a duration is in-flight.

media/cast/sender/rtp_timestamp_helper.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 MEDIA_CAST_SENDER_RTP_TIMESTAMP_HELPER_H_
-#define MEDIA_CAST_SENDER_RTP_TIMESTAMP_HELPER_H_
-
-#include "base/basictypes.h"
-#include "base/time/time.h"
-
-namespace media {
-namespace cast {
-
-// A helper class used to convert current time ticks into RTP timestamp.
-class RtpTimestampHelper {
- public:
-  explicit RtpTimestampHelper(int frequency);
-  ~RtpTimestampHelper();
-
-  // Compute a RTP timestamp using current time, last encoded time and
-  // last encoded RTP timestamp.
-  // Return true if |rtp_timestamp| is computed.
-  bool GetCurrentTimeAsRtpTimestamp(const base::TimeTicks& now,
-                                    uint32* rtp_timestamp) const;
-
-  // Store the capture time and the corresponding RTP timestamp for the
-  // last encoded frame.
-  void StoreLatestTime(base::TimeTicks capture_time, uint32 rtp_timestamp);
-
- private:
-  int frequency_;
-  base::TimeTicks last_capture_time_;
-  uint32 last_rtp_timestamp_;
-
-  DISALLOW_COPY_AND_ASSIGN(RtpTimestampHelper);
-};
-
-}  // namespace cast
-}  // namespace media
-
-#endif  // MEDIA_CAST_SENDER_RTP_TIMESTAMP_HELPER_H_