Reland Move fake_audio_device to its own target.

webrtc/modules/rtp_rtcp/source/nack_rtx_unittest.cc

Index: webrtc/modules/rtp_rtcp/source/nack_rtx_unittest.cc
diff --git a/webrtc/modules/rtp_rtcp/source/nack_rtx_unittest.cc b/webrtc/modules/rtp_rtcp/source/nack_rtx_unittest.cc
index d772753fa54f8ea6681aa3274ce1790f24a32f1c..63378905d1254a7cb5925d28ae11e48de39930e4 100644
--- a/webrtc/modules/rtp_rtcp/source/nack_rtx_unittest.cc
+++ b/webrtc/modules/rtp_rtcp/source/nack_rtx_unittest.cc
@@ -58,7 +58,7 @@ class TestRtpFeedback : public NullRtpFeedback {
   explicit TestRtpFeedback(RtpRtcp* rtp_rtcp) : rtp_rtcp_(rtp_rtcp) {}
   virtual ~TestRtpFeedback() {}
 
-  void OnIncomingSSRCChanged(const uint32_t ssrc) override {
+  void OnIncomingSSRCChanged(uint32_t ssrc) override {
     rtp_rtcp_->SetRemoteSSRC(ssrc);
   }