Pass network config constraint as base64 to avoid mangling bytes

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMediaConstraints.h

Index: webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMediaConstraints.h
diff --git a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMediaConstraints.h b/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMediaConstraints.h
index b58fa3e74c8a4229d84d28c255ed0e2f858474db..458bf822f55f9fde5f3101566dc9ee80d28b7c96 100644
--- a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMediaConstraints.h
+++ b/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMediaConstraints.h
@@ -39,6 +39,11 @@ RTC_EXPORT
     (nullable NSDictionary<NSString *, NSString *> *)optional
     NS_DESIGNATED_INITIALIZER;
 
+/** Add a new constraint with raw data/bytes. */

[tkchin_webrtc, 2017/02/02 19:04:53]

nit: add a comment like:
Some constraint values require arbitrary bytes instead of a UTF-8 string. In
particular, some constraints take the form of a serialized proto, which is
binary. This is a temporary interface until we determine a better solution.

+- (void)addConstraintForKey:(NSString *)key
+                       data:(NSData *)data
+                isMandatory:(BOOL)isMandatory;
+
 @end
 
 NS_ASSUME_NONNULL_END