AppRTCDemo file logging.

Adds logging macros to log logs to a file. Undeletes CircularFileStream
for that purpose.

BUG=
R=jiayl@webrtc.org, pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1217473011 .

Cr-Commit-Position: refs/heads/master@{#9582}
diff --git a/talk/examples/objc/AppRTCDemo/ARDSignalingMessage.m b/talk/examples/objc/AppRTCDemo/ARDSignalingMessage.m
index e9fb09a..dc00e8f 100644
--- a/talk/examples/objc/AppRTCDemo/ARDSignalingMessage.m
+++ b/talk/examples/objc/AppRTCDemo/ARDSignalingMessage.m
@@ -27,6 +27,7 @@
 
 #import "ARDSignalingMessage.h"
 
+#import "ARDLogging.h"
 #import "ARDUtilities.h"
 #import "RTCICECandidate+JSON.h"
 #import "RTCSessionDescription+JSON.h"
@@ -52,7 +53,7 @@
 + (ARDSignalingMessage *)messageFromJSONString:(NSString *)jsonString {
   NSDictionary *values = [NSDictionary dictionaryWithJSONString:jsonString];
   if (!values) {
-    NSLog(@"Error parsing signaling message JSON.");
+    ARDLog(@"Error parsing signaling message JSON.");
     return nil;
   }
 
@@ -71,7 +72,7 @@
   } else if ([typeString isEqualToString:@"bye"]) {
     message = [[ARDByeMessage alloc] init];
   } else {
-    NSLog(@"Unexpected type: %@", typeString);
+    ARDLog(@"Unexpected type: %@", typeString);
   }
   return message;
 }