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/libjingle.gyp b/talk/libjingle.gyp
index 9de1c9b..3c0f26e 100755
--- a/talk/libjingle.gyp
+++ b/talk/libjingle.gyp
@@ -240,6 +240,7 @@
             'app/webrtc/objc/RTCDataChannel.mm',
             'app/webrtc/objc/RTCEnumConverter.h',
             'app/webrtc/objc/RTCEnumConverter.mm',
+            'app/webrtc/objc/RTCFileLogger.mm',
             'app/webrtc/objc/RTCI420Frame+Internal.h',
             'app/webrtc/objc/RTCI420Frame.mm',
             'app/webrtc/objc/RTCICECandidate+Internal.h',
@@ -280,6 +281,7 @@
             'app/webrtc/objc/public/RTCAudioSource.h',
             'app/webrtc/objc/public/RTCAudioTrack.h',
             'app/webrtc/objc/public/RTCDataChannel.h',
+            'app/webrtc/objc/public/RTCFileLogger.h',
             'app/webrtc/objc/public/RTCI420Frame.h',
             'app/webrtc/objc/public/RTCICECandidate.h',
             'app/webrtc/objc/public/RTCICEServer.h',