Add UMA for tracking which BWE versions are in use.

webrtc/modules/remote_bitrate_estimator/bwe_defines.cc

Index: webrtc/modules/remote_bitrate_estimator/bwe_defines.cc
diff --git a/webrtc/modules/audio_coding/neteq/packet.cc b/webrtc/modules/remote_bitrate_estimator/bwe_defines.cc
similarity index 79%
copy from webrtc/modules/audio_coding/neteq/packet.cc
copy to webrtc/modules/remote_bitrate_estimator/bwe_defines.cc
index 8a19fe4d5923d5e22a5b485600c6da0c5f3856ba..3587ebf744b9925525f0e08bab3fb75a200799ff 100644
--- a/webrtc/modules/audio_coding/neteq/packet.cc
+++ b/webrtc/modules/remote_bitrate_estimator/bwe_defines.cc
@@ -7,13 +7,7 @@
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
-
-#include "webrtc/modules/audio_coding/neteq/packet.h"
-
 namespace webrtc {
 
-Packet::Packet() = default;
-
-Packet::~Packet() = default;
-
+const char* kBweTypeHistogram = "WebRTC.BWE.Types";
 }  // namespace webrtc