Add RTCEventLog API to ObjC.

webrtc/examples/objc/AppRTCDemo/ARDAppClient.m

Index: webrtc/examples/objc/AppRTCDemo/ARDAppClient.m
diff --git a/webrtc/examples/objc/AppRTCDemo/ARDAppClient.m b/webrtc/examples/objc/AppRTCDemo/ARDAppClient.m
index 8fb1841e391a16eb814235c21abd7a4dcc781eda..eb4ff5302f99b270011e24a09ac07cc747100d3f 100644
--- a/webrtc/examples/objc/AppRTCDemo/ARDAppClient.m
+++ b/webrtc/examples/objc/AppRTCDemo/ARDAppClient.m
@@ -55,8 +55,10 @@ static NSString * const kARDVideoTrackId = @"ARDAMSv0";
 
 // TODO(tkchin): Remove guard once rtc_sdk_common_objc compiles on Mac.
 #if defined(WEBRTC_IOS)
-// TODO(tkchin): Add this as a UI option.
+// TODO(tkchin): Add these as UI options.
 static BOOL const kARDAppClientEnableTracing = NO;
+static BOOL const kARDAppClientEnableRtcEventLog = YES;
+static int64_t const kARDAppClientRtcEventLogMaxSizeInBytes = 5e6;  // 5 MB.
 #endif
 
 // We need a proxy to NSTimer because it causes a strong retain cycle. When
@@ -227,11 +229,7 @@ static BOOL const kARDAppClientEnableTracing = NO;
 
 #if defined(WEBRTC_IOS)
   if (kARDAppClientEnableTracing) {
-    NSArray *paths = NSSearchPathForDirectoriesInDomains(
-        NSDocumentDirectory, NSUserDomainMask, YES);
-    NSString *documentsDirPath = paths.firstObject;
-    NSString *filePath =
-        [documentsDirPath stringByAppendingPathComponent:@"webrtc-trace.txt"];
+    NSString *filePath = [self documentsFilePathForFileName:@"webrtc-trace.txt"];
     RTCStartInternalCapture(filePath);
   }
 #endif
@@ -314,6 +312,7 @@ static BOOL const kARDAppClientEnableTracing = NO;
   self.state = kARDAppClientStateDisconnected;
 #if defined(WEBRTC_IOS)
   RTCStopInternalCapture();
+  [_factory stopRtcEventLog];

[Chuck, 2016/06/14 14:01:17]

Do you need the #if guards here?

[tkchin_webrtc, 2016/06/14 17:40:59]

Prob not.

[Chuck, 2016/06/14 19:36:44]

I think I confused myself, I didn't see them in the original CL (since they were
already there), and was actually suggesting to add them if you needed them. 

 #endif
 }
 
@@ -498,6 +497,20 @@ static BOOL const kARDAppClientEnableTracing = NO;
 
 #pragma mark - Private
 
+#if defined(WEBRTC_IOS)
+
+- (NSString *)documentsFilePathForFileName:(NSString *)fileName {
+  NSParameterAssert(fileName.length);
+  NSArray *paths = NSSearchPathForDirectoriesInDomains(
+      NSDocumentDirectory, NSUserDomainMask, YES);
+  NSString *documentsDirPath = paths.firstObject;
+  NSString *filePath =
+      [documentsDirPath stringByAppendingPathComponent:fileName];
+  return filePath;
+}
+
+#endif
+
 - (BOOL)hasJoinedRoomServerRoom {
   return _clientId.length;
 }
@@ -513,6 +526,15 @@ static BOOL const kARDAppClientEnableTracing = NO;
   }
   self.state = kARDAppClientStateConnected;
 
+#if defined(WEBRTC_IOS)
+  // Start event log.
+  if (kARDAppClientEnableRtcEventLog) {
+    NSString *filePath = [self documentsFilePathForFileName:@"webrtc-rtceventlog"];
+    [_factory startRtcEventLogWithFilePath:filePath

[Chuck, 2016/06/14 14:01:17]

Your comment suggests this is temporary, but should you check the return value
here and log the result?

[tkchin_webrtc, 2016/06/14 17:40:59]

Done.

+                            maxSizeInBytes:kARDAppClientRtcEventLogMaxSizeInBytes];
+  }
+#endif
+
   // Create peer connection.
   RTCMediaConstraints *constraints = [self defaultPeerConnectionConstraints];
   RTCConfiguration *config = [[RTCConfiguration alloc] init];