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.cc

@@ -13,6 +13,7 @@
 #include <assert.h>  // assert
 #include <string.h>  // memset
 
+#include "webrtc/modules/rtp_rtcp/source/rtcp_packet/transport_feedback.h"
 #include "webrtc/modules/rtp_rtcp/source/rtp_utility.h"
 
 namespace webrtc {
@@ -36,8 +37,7 @@ RTCPPacketInformation::RTCPPacketInformation()
       rtp_timestamp(0),
       xr_originator_ssrc(0),
       xr_dlrr_item(false),
-      VoIPMetric(NULL) {
-}
+      VoIPMetric(nullptr) {}
 
 RTCPPacketInformation::~RTCPPacketInformation()
 {