Use AggressiveConfiguration as the default configuration in IOS

webrtc/api/peerconnectioninterface.h

 /*
  *  Copyright 2012 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 229 matching lines @@
     // methods for all settings which are of interest to applications,
     // Chrome in particular.
 
     // A configuration that is safer to use, despite it may not have the best
     // performance.
     static RTCConfiguration SafeConfiguration() { return RTCConfiguration(); }
 
     // An aggressive configuration that has better performance, although it
     // may be riskier and may need extra support in the application.
     static RTCConfiguration AggressiveConfiguration() {
-      RTCConfiguration config;
-      config.redetermine_role_on_ice_restart = false;
-      return config;
+      return RTCConfiguration(true);
+    }
+
+    RTCConfiguration() = default;
+    RTCConfiguration(bool aggressive) {
+      if (aggressive) {
+        redetermine_role_on_ice_restart = false;
+      }

[pthatcher1, 2016/09/01 07:05:44]

I can understand why you would want to have a constructor with a parameter
instead of a static method.  But could we at least use an enum instead of a
bool?

Then we could have:

RTCConfiguration(AGGRESSIVE)
or
RTCConfiguration(SAFE)

which is much easier to read than RTCConfiguration(true), and gives more
flexibility in the future.  

[honghaiz3, 2016/09/01 16:07:50]

Done.

     }
 
     bool dscp() { return media_config.enable_dscp; }
     void set_dscp(bool enable) { media_config.enable_dscp = enable; }
 
     // TODO(nisse): The corresponding flag in MediaConfig and
     // elsewhere should be renamed enable_cpu_adaptation.
     bool cpu_adaptation() {
       return media_config.video.enable_cpu_overuse_detection;
     }
@@ skipping 489 matching lines @@
     cricket::WebRtcVideoEncoderFactory* encoder_factory,
     cricket::WebRtcVideoDecoderFactory* decoder_factory) {
   return CreatePeerConnectionFactory(
       worker_and_network_thread, worker_and_network_thread, signaling_thread,
       default_adm, encoder_factory, decoder_factory);
 }
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_PEERCONNECTIONINTERFACE_H_