Add video codec setting to AppRTCMobile on iOS.

List items in settings menu no longer stay selected. Checkmarks are now
added to the selected options before the view appears.

BUG=webrtc:7316
TBR=denicija

Review-Url: https://codereview.webrtc.org/2735303004
Cr-Commit-Position: refs/heads/master@{#17296}
diff --git a/webrtc/examples/objc/AppRTCMobile/ios/ARDVideoCallViewController.m b/webrtc/examples/objc/AppRTCMobile/ios/ARDVideoCallViewController.m
index 9e17951..f58ee66 100644
--- a/webrtc/examples/objc/AppRTCMobile/ios/ARDVideoCallViewController.m
+++ b/webrtc/examples/objc/AppRTCMobile/ios/ARDVideoCallViewController.m
@@ -44,9 +44,11 @@
       shouldUseLevelControl:(BOOL)shouldUseLevelControl
                    delegate:(id<ARDVideoCallViewControllerDelegate>)delegate {
   if (self = [super init]) {
-    _delegate = delegate;
-    _client = [[ARDAppClient alloc] initWithDelegate:self];
     ARDSettingsModel *settingsModel = [[ARDSettingsModel alloc] init];
+    NSString* videoCodec = [settingsModel currentVideoCodecSettingFromStore];
+    _delegate = delegate;
+    _client = [[ARDAppClient alloc] initWithDelegate:self
+                                    preferVideoCodec:videoCodec];
     RTCMediaConstraints *cameraConstraints = [[RTCMediaConstraints alloc]
         initWithMandatoryConstraints:nil
                  optionalConstraints:[settingsModel