Reland of Split iOS sdk in to separate targets

webrtc/sdk/objc/Framework/Classes/Common/RTCFieldTrials.mm

 /*
  *  Copyright 2016 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.
  */
 
@@ skipping 47 matching lines @@
   size_t len = fieldTrialInitString.length + 1;
   gFieldTrialInitString.reset(new char[len]);
   if (![fieldTrialInitString getCString:gFieldTrialInitString.get()
                               maxLength:len
                                encoding:NSUTF8StringEncoding]) {
     RTCLogError(@"Failed to convert field trial string.");
     return;
   }
   webrtc::field_trial::InitFieldTrialsFromString(gFieldTrialInitString.get());
 }