Update iOS AppRTCDemo to use the updated Objective-C API.

webrtc/examples/objc/AppRTCDemo/RTCMediaConstraints+JSON.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.
  */
 
 #import "RTCMediaConstraints+JSON.h"
 
-#import "RTCPair.h"
-
 static NSString const *kRTCMediaConstraintsMandatoryKey = @"mandatory";
 
 @implementation RTCMediaConstraints (JSON)
 
 + (RTCMediaConstraints *)constraintsFromJSONDictionary:
     (NSDictionary *)dictionary {
   NSDictionary *mandatory = dictionary[kRTCMediaConstraintsMandatoryKey];
-  NSMutableArray *mandatoryContraints =
-      [NSMutableArray arrayWithCapacity:[mandatory count]];
+  NSMutableDictionary *mandatoryContraints =
+      [NSMutableDictionary dictionaryWithCapacity:[mandatory count]];
   [mandatory enumerateKeysAndObjectsUsingBlock:^(
       id key, id obj, BOOL *stop) {
-    [mandatoryContraints addObject:[[RTCPair alloc] initWithKey:key
-                                                          value:obj]];
+    mandatoryContraints[key] = obj;
   }];
   // TODO(tkchin): figure out json formats for optional constraints.
   RTCMediaConstraints *constraints =
       [[RTCMediaConstraints alloc]
           initWithMandatoryConstraints:mandatoryContraints
                    optionalConstraints:nil];
   return constraints;
 }
 
 @end