Update API for Objective-C RTCSessionDescription.

webrtc/api/api.gyp

 # 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.
 
 {
   'includes': [ '../build/common.gypi', ],
   'conditions': [
     ['OS=="ios"', {
       'targets': [
         {
           'target_name': 'rtc_api_objc',
           'type': 'static_library',
           'dependencies': [
             '<(webrtc_root)/base/base.gyp:rtc_base_objc',
             '../../talk/libjingle.gyp:libjingle_peerconnection',
           ],
           'sources': [
             'objc/RTCIceCandidate+Private.h',
             'objc/RTCIceCandidate.h',
             'objc/RTCIceCandidate.mm',
             'objc/RTCIceServer+Private.h',
             'objc/RTCIceServer.h',
             'objc/RTCIceServer.mm',
+            'objc/RTCSessionDescription+Private.h',
+            'objc/RTCSessionDescription.h',
+            'objc/RTCSessionDescription.mm',
           ],
           'xcode_settings': {
             'CLANG_ENABLE_OBJC_ARC': 'YES',
             'CLANG_WARN_OBJC_MISSING_PROPERTY_SYNTHESIS': 'YES',
             'GCC_PREFIX_HEADER': 'objc/WebRTC-Prefix.pch',
           },
         }
       ],
     }], # OS=="ios"
   ],
 }