Replace uses of raw uint32's with a type-checked RtpTimeTicks data type.

media/cast/net/rtcp/receiver_rtcp_event_subscriber.h

Index: media/cast/net/rtcp/receiver_rtcp_event_subscriber.h
diff --git a/media/cast/net/rtcp/receiver_rtcp_event_subscriber.h b/media/cast/net/rtcp/receiver_rtcp_event_subscriber.h
index 248f07a74ea5a626613c2cbaf2bdf9a024f38b3d..cd90842ab2b705b7bba3c93906736ed7e8adf77f 100644
--- a/media/cast/net/rtcp/receiver_rtcp_event_subscriber.h
+++ b/media/cast/net/rtcp/receiver_rtcp_event_subscriber.h
@@ -31,8 +31,8 @@ static const size_t kMaxEventsPerRTCP = 20;
 //   timestamp) up to the size limit.
 class ReceiverRtcpEventSubscriber : public RawEventSubscriber {
  public:
-  typedef std::pair<RtpTimestamp, RtcpEvent> RtcpEventPair;
-  typedef std::vector<std::pair<RtpTimestamp, RtcpEvent> > RtcpEvents;
+  typedef std::pair<RtpTimeTicks, RtcpEvent> RtcpEventPair;
+  typedef std::vector<std::pair<RtpTimeTicks, RtcpEvent>> RtcpEvents;
 
   // |max_size_to_retain|: The object will keep up to |max_size_to_retain|
   // events