Cast: Simplify code path for RTCP sender report

media/cast/rtp_timestamp_helper.cc

Index: media/cast/rtp_timestamp_helper.cc
diff --git a/media/cast/rtp_timestamp_helper.cc b/media/cast/rtp_timestamp_helper.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a0c56c09eabdde82e7c6d4e1208813c672fb64ce
--- /dev/null
+++ b/media/cast/rtp_timestamp_helper.cc
@@ -0,0 +1,35 @@
+// 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.
+
+#include "media/cast/rtp_timestamp_helper.h"
+
+namespace media {
+namespace cast {
+
+RtpTimestampHelper::RtpTimestampHelper(int frequency)
+    : frequency_(frequency),
+      last_rtp_timestamp_(0) {
+}
+
+RtpTimestampHelper::~RtpTimestampHelper() {
+}
+
+bool RtpTimestampHelper::GetCurrentTimeAsRtpTimestamp(
+    const base::TimeTicks& now, uint32* rtp_timestamp) const {
+  if (last_capture_time_.is_null())
+    return false;
+  base::TimeDelta elapsed_time = now - last_capture_time_;
+  *rtp_timestamp = last_rtp_timestamp_ + elapsed_time.InMilliseconds() *
+      frequency_ / base::Time::kMillisecondsPerSecond;
+  return true;
+}
+
+void RtpTimestampHelper::StoreLatestTime(
+    base::TimeTicks capture_time, uint32 rtp_timestamp) {
+  last_capture_time_ = capture_time;
+  last_rtp_timestamp_ = rtp_timestamp;
+}
+
+}  // namespace cast
+}  // namespace media