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/ARDAppClient.m b/talk/examples/objc/AppRTCDemo/ARDAppClient.m
index 5b905c6..e043da2 100644
--- a/talk/examples/objc/AppRTCDemo/ARDAppClient.m
+++ b/talk/examples/objc/AppRTCDemo/ARDAppClient.m
@@ -32,17 +32,16 @@
 #endif
 #import "RTCFileLogger.h"
 #import "RTCICEServer.h"
+#import "RTCLogging.h"
 #import "RTCMediaConstraints.h"
 #import "RTCMediaStream.h"
 #import "RTCPair.h"
 #import "RTCPeerConnectionInterface.h"
 #import "RTCVideoCapturer.h"
-#import "RTCAVFoundationVideoSource.h"
 
 #import "ARDAppEngineClient.h"
 #import "ARDCEODTURNClient.h"
 #import "ARDJoinResponse.h"
-#import "ARDLogging.h"
 #import "ARDMessageResponse.h"
 #import "ARDSDPUtils.h"
 #import "ARDSignalingMessage.h"
@@ -162,7 +161,8 @@
   [_turnClient requestServersWithCompletionHandler:^(NSArray *turnServers,
                                                      NSError *error) {
     if (error) {
-      ARDLog("Error retrieving TURN servers: %@", error.localizedDescription);
+      RTCLogError("Error retrieving TURN servers: %@",
+                  error.localizedDescription);
     }
     ARDAppClient *strongSelf = weakSelf;
     [strongSelf.iceServers addObjectsFromArray:turnServers];
@@ -181,12 +181,12 @@
     NSError *joinError =
         [[strongSelf class] errorForJoinResultType:response.result];
     if (joinError) {
-      ARDLog(@"Failed to join room:%@ on room server.", roomId);
+      RTCLogError(@"Failed to join room:%@ on room server.", roomId);
       [strongSelf disconnect];
       [strongSelf.delegate appClient:strongSelf didError:joinError];
       return;
     }
-    ARDLog(@"Joined room:%@ on room server.", roomId);
+    RTCLog(@"Joined room:%@ on room server.", roomId);
     strongSelf.roomId = response.roomId;
     strongSelf.clientId = response.clientId;
     strongSelf.isInitiator = response.isInitiator;
@@ -278,13 +278,13 @@
 
 - (void)peerConnection:(RTCPeerConnection *)peerConnection
     signalingStateChanged:(RTCSignalingState)stateChanged {
-  ARDLog(@"Signaling state changed: %d", stateChanged);
+  RTCLog(@"Signaling state changed: %d", stateChanged);
 }
 
 - (void)peerConnection:(RTCPeerConnection *)peerConnection
            addedStream:(RTCMediaStream *)stream {
   dispatch_async(dispatch_get_main_queue(), ^{
-    ARDLog(@"Received %lu video tracks and %lu audio tracks",
+    RTCLog(@"Received %lu video tracks and %lu audio tracks",
         (unsigned long)stream.videoTracks.count,
         (unsigned long)stream.audioTracks.count);
     if (stream.videoTracks.count) {
@@ -296,17 +296,17 @@
 
 - (void)peerConnection:(RTCPeerConnection *)peerConnection
         removedStream:(RTCMediaStream *)stream {
-  ARDLog(@"Stream was removed.");
+  RTCLog(@"Stream was removed.");
 }
 
 - (void)peerConnectionOnRenegotiationNeeded:
     (RTCPeerConnection *)peerConnection {
-  ARDLog(@"WARNING: Renegotiation needed but unimplemented.");
+  RTCLog(@"WARNING: Renegotiation needed but unimplemented.");
 }
 
 - (void)peerConnection:(RTCPeerConnection *)peerConnection
     iceConnectionChanged:(RTCICEConnectionState)newState {
-  ARDLog(@"ICE state changed: %d", newState);
+  RTCLog(@"ICE state changed: %d", newState);
   dispatch_async(dispatch_get_main_queue(), ^{
     [_delegate appClient:self didChangeConnectionState:newState];
   });
@@ -314,7 +314,7 @@
 
 - (void)peerConnection:(RTCPeerConnection *)peerConnection
     iceGatheringChanged:(RTCICEGatheringState)newState {
-  ARDLog(@"ICE gathering state changed: %d", newState);
+  RTCLog(@"ICE gathering state changed: %d", newState);
 }
 
 - (void)peerConnection:(RTCPeerConnection *)peerConnection
@@ -339,7 +339,7 @@
                           error:(NSError *)error {
   dispatch_async(dispatch_get_main_queue(), ^{
     if (error) {
-      ARDLog(@"Failed to create session description. Error: %@", error);
+      RTCLogError(@"Failed to create session description. Error: %@", error);
       [self disconnect];
       NSDictionary *userInfo = @{
         NSLocalizedDescriptionKey: @"Failed to create session description.",
@@ -368,7 +368,7 @@
     didSetSessionDescriptionWithError:(NSError *)error {
   dispatch_async(dispatch_get_main_queue(), ^{
     if (error) {
-      ARDLog(@"Failed to set session description. Error: %@", error);
+      RTCLogError(@"Failed to set session description. Error: %@", error);
       [self disconnect];
       NSDictionary *userInfo = @{
         NSLocalizedDescriptionKey: @"Failed to set session description.",