Address tkchin's comments on RTCCameraVideoCapturer.

webrtc/sdk/objc/Framework/Classes/RTCDispatcher.m

Index: webrtc/sdk/objc/Framework/Classes/RTCDispatcher.m
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCDispatcher.m b/webrtc/sdk/objc/Framework/Classes/RTCDispatcher.m
index 94176ac6d810d4890addced9ad379d515f6418b4..530e51a3c94bc812425e5c00696245781f5d819d 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCDispatcher.m
+++ b/webrtc/sdk/objc/Framework/Classes/RTCDispatcher.m
@@ -33,6 +33,17 @@ static dispatch_queue_t kCaptureSessionQueue = nil;
   dispatch_async(queue, block);
 }
 
++ (BOOL)isOnQueueForType:(RTCDispatcherQueueType)dispatchType {
+  dispatch_queue_t targetQueue = [self dispatchQueueForType:dispatchType];
+  const char* targetLabel = dispatch_queue_get_label(targetQueue);
+  const char* currentLabel = dispatch_queue_get_label(DISPATCH_CURRENT_QUEUE_LABEL);
+
+  NSAssert(strlen(targetLabel) > 0, @"Label is required for the target queue.");
+  NSAssert(strlen(currentLabel) > 0, @"Label is required for the current queue.");
+
+  return strcmp(targetLabel, currentLabel) == 0;
+}
+
 #pragma mark - Private
 
 + (dispatch_queue_t)dispatchQueueForType:(RTCDispatcherQueueType)dispatchType {