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

webrtc/examples/objc/AppRTCMobile/ARDAppClient.m

Index: webrtc/examples/objc/AppRTCMobile/ARDAppClient.m
diff --git a/webrtc/examples/objc/AppRTCMobile/ARDAppClient.m b/webrtc/examples/objc/AppRTCMobile/ARDAppClient.m
index 1020621cc1bd2b91340963ac20609688aaacd8f6..ecf65286d8ad09a94f75ce1555bba2bedb348648 100644
--- a/webrtc/examples/objc/AppRTCMobile/ARDAppClient.m
+++ b/webrtc/examples/objc/AppRTCMobile/ARDAppClient.m
@@ -101,6 +101,7 @@ static int64_t const kARDAppClientRtcEventLogMaxSizeInBytes = 5e6;  // 5 MB.
 @implementation ARDAppClient {
   RTCFileLogger *_fileLogger;
   ARDTimerProxy *_statsTimer;
+  RTCMediaConstraints *_defaultMediaStreamConstraints;
 }
 
 @synthesize shouldGetStats = _shouldGetStats;
@@ -321,6 +322,10 @@ static int64_t const kARDAppClientRtcEventLogMaxSizeInBytes = 5e6;  // 5 MB.
 #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
@@ -737,18 +742,14 @@ static int64_t const kARDAppClientRtcEventLogMaxSizeInBytes = 5e6;  // 5 MB.
    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 {