Make ECDSA default for RTCPeerConnection

webrtc/api/objc/RTCSessionDescription.mm

 /*
  *  Copyright 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.
  */
 
@@ skipping 68 matching lines @@
 
 + (RTCSdpType)typeForString:(const std::string &)string {
   if (string == webrtc::SessionDescriptionInterface::kOffer) {
     return RTCSdpTypeOffer;
   } else if (string == webrtc::SessionDescriptionInterface::kPrAnswer) {
     return RTCSdpTypePrAnswer;
   } else if (string == webrtc::SessionDescriptionInterface::kAnswer) {
     return RTCSdpTypeAnswer;
   } else {
     RTC_NOTREACHED();
+    return RTCSdpTypeOffer;
   }
 }
 
 @end