Fix building iOS SDK static libraries.

webrtc/build/ios/objc_app.gypi

 # 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.
 
 # Include this .gypi in an ObjC target's definition to allow it to be
 # used as an iOS or OS/X application.
 
 {
   'variables': {
     'infoplist_file': './objc_app.plist',
   },
   'dependencies': [
     '<(webrtc_root)/system_wrappers/system_wrappers.gyp:field_trial_default',
+    '<(webrtc_root)/system_wrappers/system_wrappers.gyp:metrics_default',
   ],
   'mac_bundle': 1,
   'mac_bundle_resources': [
     '<(infoplist_file)',
   ],
   # The plist is listed above so that it appears in XCode's file list,
   # but we don't actually want to bundle it.
   'mac_bundle_resources!': [
     '<(infoplist_file)',
   ],
   'xcode_settings': {
     'CLANG_ENABLE_OBJC_ARC': 'YES',
     'INFOPLIST_FILE': '<(infoplist_file)',
   },
 }