Cast: Simplify code path for RTCP sender report

media/cast/rtp_timestamp_helper.h

Index: media/cast/rtp_timestamp_helper.h
diff --git a/media/cast/rtp_timestamp_helper.h b/media/cast/rtp_timestamp_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..b9c650c506317064c333357c83c1d44a40ab1d7d
--- /dev/null
+++ b/media/cast/rtp_timestamp_helper.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 MEDIA_CAST_RTP_TIMESTAMP_HELPER_H_
+#define MEDIA_CAST_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_CAST_DEFINES_H_