Address tkchin's comments on RTCCameraVideoCapturer.

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

Index: webrtc/sdk/objc/Framework/Classes/RTCCameraVideoCapturer.m
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCCameraVideoCapturer.m b/webrtc/sdk/objc/Framework/Classes/RTCCameraVideoCapturer.m
index 6545b2f0d9f2c0b7ba836a58c71b55e316dfebc2..35f15d2ec2d6369e1acca009dae7244636b89451 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCCameraVideoCapturer.m
+++ b/webrtc/sdk/objc/Framework/Classes/RTCCameraVideoCapturer.m
@@ -361,6 +361,8 @@ static inline BOOL IsMediaSubTypeSupported(FourCharCode mediaSubType) {
 #pragma mark - Private, called inside capture queue
 
 - (void)updateDeviceCaptureFormat:(AVCaptureDeviceFormat *)format fps:(int)fps {
+  NSAssert([RTCDispatcher isOnQueueForType:RTCDispatcherTypeCaptureSession],
+           @"updateDeviceCaptureFormat must be called on the capture queue.");
   @try {
     _currentDevice.activeFormat = format;
     _currentDevice.activeVideoMinFrameDuration = CMTimeMake(1, fps);
@@ -371,6 +373,8 @@ static inline BOOL IsMediaSubTypeSupported(FourCharCode mediaSubType) {
 }
 
 - (void)reconfigureCaptureSessionInput {
+  NSAssert([RTCDispatcher isOnQueueForType:RTCDispatcherTypeCaptureSession],
+           @"reconfigureCaptureSessionInput must be called on the capture queue.");
   NSError *error = nil;
   AVCaptureDeviceInput *input =
       [AVCaptureDeviceInput deviceInputWithDevice:_currentDevice error:&error];
@@ -390,6 +394,8 @@ static inline BOOL IsMediaSubTypeSupported(FourCharCode mediaSubType) {
 }
 
 - (void)updateOrientation {
+  NSAssert([RTCDispatcher isOnQueueForType:RTCDispatcherTypeCaptureSession],
+           @"updateOrientation must be called on the capture queue.");
 #if TARGET_OS_IPHONE
   BOOL usingFrontCamera = _currentDevice.position == AVCaptureDevicePositionFront;
   switch ([UIDevice currentDevice].orientation) {