Compile rtc_api_objc on Mac.

webrtc/api/objc/RTCMediaConstraints.mm

 /*
  *  Copyright 2015 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 20 matching lines @@
 
 const MediaConstraintsInterface::Constraints&
 MediaConstraints::GetOptional() const {
   return optional_;
 }
 
 }  // namespace webrtc
 
 
 @implementation RTCMediaConstraints {
-  NSDictionary<NSString *, NSString *> *_mandatory;
-  NSDictionary<NSString *, NSString *> *_optional;
+  NSDictionary/*<NSString *, NSString *>*/ *_mandatory;
+  NSDictionary/*<NSString *, NSString *>*/ *_optional;
 }
 
 - (instancetype)initWithMandatoryConstraints:
-    (NSDictionary<NSString *, NSString *> *)mandatory
+    (NSDictionary/*<NSString *, NSString *>*/ *)mandatory
                          optionalConstraints:
-    (NSDictionary<NSString *, NSString *> *)optional {
+    (NSDictionary/*<NSString *, NSString *>*/ *)optional {
   if (self = [super init]) {
     _mandatory = [[NSDictionary alloc] initWithDictionary:mandatory
                                                 copyItems:YES];
     _optional = [[NSDictionary alloc] initWithDictionary:optional
                                                copyItems:YES];
   }
   return self;
 }
 
 - (NSString *)description {
@@ skipping 10 matching lines @@
   webrtc::MediaConstraintsInterface::Constraints optional =
       [[self class] nativeConstraintsForConstraints:_optional];
 
   webrtc::MediaConstraints *nativeConstraints =
       new webrtc::MediaConstraints(mandatory, optional);
   return rtc::scoped_ptr<webrtc::MediaConstraints>(nativeConstraints);
 }
 
 + (webrtc::MediaConstraintsInterface::Constraints)
     nativeConstraintsForConstraints:
-        (NSDictionary<NSString *, NSString *> *)constraints {
+        (NSDictionary/*<NSString *, NSString *>*/ *)constraints {
   webrtc::MediaConstraintsInterface::Constraints nativeConstraints;
   for (NSString *key in constraints) {
     NSAssert([key isKindOfClass:[NSString class]],
              @"%@ is not an NSString.", key);
-    NSAssert([constraints[key] isKindOfClass:[NSString class]],
-             @"%@ is not an NSString.", constraints[key]);
+    NSString *value = [constraints objectForKey:key];
+    NSAssert([value isKindOfClass:[NSString class]],
+             @"%@ is not an NSString.", value);
     nativeConstraints.push_back(webrtc::MediaConstraintsInterface::Constraint(
-        key.stdString, constraints[key].stdString));
+        key.stdString, value.stdString));
   }
   return nativeConstraints;
 }
 
 @end