Add an empty libjingle_peerconnection_metrics_default_jni target.

webrtc/api/BUILD.gn

 # Copyright (c) 2015 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.
 
 import("../build/webrtc.gni")
 if (is_android) {
@@ skipping 212 matching lines @@
       deps += [ "$rtc_libyuv_dir" ]
       public_deps = [
         "$rtc_libyuv_dir",
       ]
     } else {
       # Need to add a directory normally exported by libyuv.
       include_dirs = [ "$rtc_libyuv_dir/include" ]
     }
   }
 
+  rtc_static_library("libjingle_peerconnection_metrics_default_jni") {
+  }
+
   rtc_shared_library("libjingle_peerconnection_so") {
     sources = [
       "android/jni/jni_onload.cc",
     ]
 
     suppressed_configs += [ "//build/config/android:hide_native_jni_exports" ]
 
     deps = [
       ":libjingle_peerconnection",
       ":libjingle_peerconnection_jni",
@@ skipping 243 matching lines @@
       deps = [
         ":libjingle_peerconnection_java",
         "../base:base_java",
         "//base:base_java",
       ]
 
       shared_libraries = [ ":libjingle_peerconnection_so" ]
     }
   }
 }