Add RTCP packet type counter (for getting statistics such as sent/received NACK and FIR).

Add counter to RTCP sender and RTCP receiver.
Add video api GetRtcpPacketTypes().

BUG=2638
R=mflodman@webrtc.org, stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/8179004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5575 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/rtp_rtcp/interface/rtp_rtcp.h

@@ -507,6 +507,13 @@ class RtpRtcp : public Module {
     */
     virtual int32_t RemoveRTCPReportBlock(const uint32_t SSRC) = 0;
 
+    /*
+    *   Get number of sent and received RTCP packet types.
+    */
+    virtual void GetRtcpPacketTypeCounters(
+        RtcpPacketTypeCounter* packets_sent,
+        RtcpPacketTypeCounter* packets_received) const = 0;
+
     /*
     *   (APP) Application specific data
     *