Reconfigure capture session in a single transaction.

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..16ddc13c9eaba1f5aaf42176a66c5444a4740e3e 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCCameraVideoCapturer.m
+++ b/webrtc/sdk/objc/Framework/Classes/RTCCameraVideoCapturer.m
@@ -378,6 +378,7 @@ static inline BOOL IsMediaSubTypeSupported(FourCharCode mediaSubType) {
     RTCLogError(@"Failed to create front camera input: %@", error.localizedDescription);
     return;
   }
+  [_captureSession beginConfiguration];
   for (AVCaptureDeviceInput *oldInput in [_captureSession.inputs copy]) {
     [_captureSession removeInput:oldInput];
   }
@@ -385,8 +386,8 @@ static inline BOOL IsMediaSubTypeSupported(FourCharCode mediaSubType) {
     [_captureSession addInput:input];
   } else {
     RTCLogError(@"Cannot add camera as an input to the session.");
-    return;
   }
+  [_captureSession commitConfiguration];
 }
 
 - (void)updateOrientation {