Fix UT failure by temporarily uncommenting

webrtc/audio/audio_send_stream.cc

Index: webrtc/audio/audio_send_stream.cc
diff --git a/webrtc/audio/audio_send_stream.cc b/webrtc/audio/audio_send_stream.cc
index d16ae181af97cd3778f76ebe728beab8932c4135..e9c74c83e63b7284b1bcb30f8689c157b881a25a 100644
--- a/webrtc/audio/audio_send_stream.cc
+++ b/webrtc/audio/audio_send_stream.cc
@@ -274,7 +274,7 @@ void AudioSendStream::OnPacketAdded(uint32_t ssrc, uint16_t seq_num) {
 
 void AudioSendStream::OnPacketFeedbackVector(
     const std::vector<PacketFeedback>& packet_feedback_vector) {
-  // TODO(elad.alon): This fails in UT; fix and uncomment.
+  // TODO(elad.alon): This fails in UT; fix and uncomment. (WebRTC issue 7405.)

[the sun, 2017/03/27 14:30:29]

Super nit: Referring to issues in this format is not so common in the code base
(3 occurencies). It is more common to add a link to the bug tracker issue, i.e.:
See https://bugs.chromium.org/p/webrtc/issues/detail?id=7405.

[elad.alon_webrtc.org, 2017/03/27 14:55:44]

Will do.

   // RTC_DCHECK(worker_thread_checker_.CalledOnValidThread());
   rtc::Optional<float> plr;
   rtc::Optional<float> rplr;