AppRTCDemo was blocking the main thread for network requests. This fixes it by making the background queue serial instead of using @synchronize to make the background operations serial.

R=fischman@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/16379004

Patch from Bridger Maxwell <bridgeyman@gmail.com>.

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6028 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/AUTHORS b/AUTHORS
index 6916016..d9bb54d 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -3,6 +3,7 @@
 
 Anil Kumar <an1kumar@gmail.com>
 Ben Strong <bstrong@gmail.com>
+Bridger Maxwell <bridgeyman@gmail.com>
 Christophe Dumez <ch.dumez@samsung.com>
 Eric Rescorla, RTFM Inc.
 Jie Mao <maojie0924@gmail.com>