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

webrtc/examples/objc/AppRTCDemo/RTCSessionDescription+JSON.m

Index: webrtc/examples/objc/AppRTCDemo/RTCSessionDescription+JSON.m
diff --git a/webrtc/examples/objc/AppRTCDemo/RTCSessionDescription+JSON.m b/webrtc/examples/objc/AppRTCDemo/RTCSessionDescription+JSON.m
index b5655e0e8224d129672d4886616896acd37d7b74..a6059f77a8a850d4613793e3ab95a2d8ba277d4c 100644
--- a/webrtc/examples/objc/AppRTCDemo/RTCSessionDescription+JSON.m
+++ b/webrtc/examples/objc/AppRTCDemo/RTCSessionDescription+JSON.m
@@ -17,15 +17,17 @@ static NSString const *kRTCSessionDescriptionSdpKey = @"sdp";
 
 + (RTCSessionDescription *)descriptionFromJSONDictionary:
     (NSDictionary *)dictionary {
-  NSString *type = dictionary[kRTCSessionDescriptionTypeKey];
+  NSString *typeString = dictionary[kRTCSessionDescriptionTypeKey];
+  RTCSdpType type = [[self class] typeForString:typeString];
   NSString *sdp = dictionary[kRTCSessionDescriptionSdpKey];
   return [[RTCSessionDescription alloc] initWithType:type sdp:sdp];
 }
 
 - (NSData *)JSONData {
+  NSString *type = [[self class] stringForType:self.type];
   NSDictionary *json = @{
-    kRTCSessionDescriptionTypeKey : self.type,
-    kRTCSessionDescriptionSdpKey : self.description
+    kRTCSessionDescriptionTypeKey : type,
+    kRTCSessionDescriptionSdpKey : self.sdp
   };
   return [NSJSONSerialization dataWithJSONObject:json options:0 error:nil];
 }