iOS: Move AppRTC logging methods to public headers.

BUG=

Review URL: https://codereview.webrtc.org/1241283004

Cr-Commit-Position: refs/heads/master@{#9629}
diff --git a/talk/examples/objc/AppRTCDemo/ARDSignalingMessage.m b/talk/examples/objc/AppRTCDemo/ARDSignalingMessage.m
index dc00e8f..4d49a2e 100644
--- a/talk/examples/objc/AppRTCDemo/ARDSignalingMessage.m
+++ b/talk/examples/objc/AppRTCDemo/ARDSignalingMessage.m
@@ -27,7 +27,8 @@
 
 #import "ARDSignalingMessage.h"
 
-#import "ARDLogging.h"
+#import "RTCLogging.h"
+
 #import "ARDUtilities.h"
 #import "RTCICECandidate+JSON.h"
 #import "RTCSessionDescription+JSON.h"
@@ -53,7 +54,7 @@
 + (ARDSignalingMessage *)messageFromJSONString:(NSString *)jsonString {
   NSDictionary *values = [NSDictionary dictionaryWithJSONString:jsonString];
   if (!values) {
-    ARDLog(@"Error parsing signaling message JSON.");
+    RTCLogError(@"Error parsing signaling message JSON.");
     return nil;
   }
 
@@ -72,7 +73,7 @@
   } else if ([typeString isEqualToString:@"bye"]) {
     message = [[ARDByeMessage alloc] init];
   } else {
-    ARDLog(@"Unexpected type: %@", typeString);
+    RTCLogError(@"Unexpected type: %@", typeString);
   }
   return message;
 }