Add UMA metrics for ICE regathering reasons.

webrtc/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 # TODO(kjellander): Rebase this to webrtc/build/common.gypi changes after r6330.
 
@@ skipping 344 matching lines @@
         "-Wno-missing-braces",
         "-Wno-sign-compare",
         "-Wno-unused-const-variable",
       ]
     }
   }
 
   rtc_test("rtc_unittests") {
     testonly = true
     sources = [
+      "api/fakemetricsobserver.cc",
       "base/array_view_unittest.cc",
       "base/atomicops_unittest.cc",
       "base/autodetectproxy_unittest.cc",
       "base/bandwidthsmoother_unittest.cc",
       "base/base64_unittest.cc",
       "base/basictypes_unittest.cc",
       "base/bind_unittest.cc",
       "base/bitbuffer_unittest.cc",
       "base/buffer_unittest.cc",
       "base/bufferqueue_unittest.cc",
@@ skipping 446 matching lines @@
       ]
 
       deps = [
         "//webrtc/api:libjingle_peerconnection_java",
         "//webrtc/api:libjingle_peerconnection_jni",
         "//webrtc/examples:AppRTCMobile_javalib",
       ]
     }
   }
 }