Add setting to AppRTCMobile for iOS, that can change capture resolution.

webrtc/examples/objc/AppRTCMobile/ARDAppClient.m

 /*
  *  Copyright 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.
  */
 
@@ skipping 83 matching lines @@
 
 - (void)timerDidFire:(NSTimer *)timer {
   _timerHandler();
 }
 
 @end
 
 @implementation ARDAppClient {
   RTCFileLogger *_fileLogger;
   ARDTimerProxy *_statsTimer;
+  RTCMediaConstraints *_defaultMediaStreamConstraints;
 }
 
 @synthesize shouldGetStats = _shouldGetStats;
 @synthesize state = _state;
 @synthesize delegate = _delegate;
 @synthesize roomServerClient = _roomServerClient;
 @synthesize channel = _channel;
 @synthesize loopbackChannel = _loopbackChannel;
 @synthesize turnClient = _turnClient;
 @synthesize peerConnection = _peerConnection;
@@ skipping 200 matching lines @@
   [_factory stopAecDump];
   [_peerConnection stopRtcEventLog];
 #endif
   _peerConnection = nil;
   self.state = kARDAppClientStateDisconnected;
 #if defined(WEBRTC_IOS)
   RTCStopInternalCapture();
 #endif
 }
 
+- (void)setDefaultMediaStreamConstraints:(RTCMediaConstraints *)mediaConstraints {

[magjed_webrtc, 2016/10/31 19:26:39]

I don't think the word 'default' is appropriate here or in the
defaultMediaStreamConstraints function anymore. How about just
setMediaStreamConstraints? 'MediaStream' is also a bit too generic, maybe
setVideoSourceConstraints or setCameraConstraints instead?

[daniela-webrtc, 2016/11/01 09:51:12]

That makes sense. Should we change the `defaultMediaAudioConstraints` as well? I
kinda like the symmetry those method have currently.

[magjed_webrtc, 2016/11/01 12:06:09]

I think we should leave the name 'defaultMediaAudioConstraints' for now. My
motivation for this is that 'defaultMediaAudioConstraints' is still a function
providing default values, similar to 'defaultVideoResolutionMediaConstraint' in
ARDMediaConstraintsModel, but this video constraints function does not provide
default values anymore. We can change the name of 'defaultMediaAudioConstraints'
and make it symmetric again once we make a similar CL like this for audio
settings.

+  _defaultMediaStreamConstraints = mediaConstraints;
+}
+
 #pragma mark - ARDSignalingChannelDelegate
 
 - (void)channel:(id<ARDSignalingChannel>)channel
     didReceiveMessage:(ARDSignalingMessage *)message {
   switch (message.type) {
     case kARDSignalingMessageTypeOffer:
     case kARDSignalingMessageTypeAnswer:
       // Offers and answers must be processed before any other message, so we
       // place them at the front of the queue.
       _hasReceivedSdp = YES;
@@ skipping 396 matching lines @@
     [_loopbackChannel registerForRoomId:_roomId clientId:@"LOOPBACK_CLIENT_ID"];
   }
 }
 
 #pragma mark - Defaults
 
  - (RTCMediaConstraints *)defaultMediaAudioConstraints {
    NSString *valueLevelControl = _shouldUseLevelControl ?
        kRTCMediaConstraintsValueTrue : kRTCMediaConstraintsValueFalse;
    NSDictionary *mandatoryConstraints = @{ kRTCMediaConstraintsLevelControl : valueLevelControl };
-   RTCMediaConstraints* constraints =
-       [[RTCMediaConstraints alloc]  initWithMandatoryConstraints:mandatoryConstraints
-                                              optionalConstraints:nil];
+   RTCMediaConstraints *constraints =
+       [[RTCMediaConstraints alloc] initWithMandatoryConstraints:mandatoryConstraints
+                                             optionalConstraints:nil];
    return constraints;
 }
 
 - (RTCMediaConstraints *)defaultMediaStreamConstraints {
-  RTCMediaConstraints* constraints =
-      [[RTCMediaConstraints alloc]
-          initWithMandatoryConstraints:nil
-                   optionalConstraints:nil];
-  return constraints;
+  return _defaultMediaStreamConstraints;
 }
 
 - (RTCMediaConstraints *)defaultAnswerConstraints {
   return [self defaultOfferConstraints];
 }
 
 - (RTCMediaConstraints *)defaultOfferConstraints {
   NSDictionary *mandatoryConstraints = @{
     @"OfferToReceiveAudio" : @"true",
     @"OfferToReceiveVideo" : @"true"
@@ skipping 75 matching lines @@
                                          code:kARDAppClientErrorInvalidRoom
                                      userInfo:@{
         NSLocalizedDescriptionKey: @"Invalid room.",
       }];
       break;
   }
   return error;
 }
 
 @end