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}
diff --git a/webrtc/modules/remote_bitrate_estimator/BUILD.gn b/webrtc/modules/remote_bitrate_estimator/BUILD.gn
index 5f0be09..99c297d 100644
--- a/webrtc/modules/remote_bitrate_estimator/BUILD.gn
+++ b/webrtc/modules/remote_bitrate_estimator/BUILD.gn
@@ -36,7 +36,11 @@
     "overuse_estimator.h",
     "remote_bitrate_estimator_abs_send_time.cc",
     "remote_bitrate_estimator_single_stream.cc",
+    "remote_estimator_proxy.cc",
+    "remote_estimator_proxy.h",
     "send_time_history.cc",
+    "transport_feedback_adapter.cc",
+    "transport_feedback_adapter.h",
   ]
 
   configs += [ "../..:common_config" ]