Reland "Wire up send-side bandwidth estimation."

Revert was patchset #8 id:140001 of https://codereview.webrtc.org/1338203003/

The culprit was RTC_DCHECK(poller_thread_->Start()); in rampup_test.cc

BUG=webrtc:4173
R=stefan@webrtc.org

Review URL: https://codereview.webrtc.org/1362303002 .

Cr-Commit-Position: refs/heads/master@{#10052}

webrtc/modules/rtp_rtcp/source/rtcp_receiver_help.h

@@ -20,6 +20,9 @@
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
+namespace rtcp {
+class TransportFeedback;
+}
 namespace RTCPHelp
 {
 
@@ -84,6 +87,8 @@ public:
     bool xr_dlrr_item;
     RTCPVoIPMetric*  VoIPMetric;
 
+    rtc::scoped_ptr<rtcp::TransportFeedback> transport_feedback_;
+
 private:
     RTC_DISALLOW_COPY_AND_ASSIGN(RTCPPacketInformation);
 };