Add unit tests for avfoundation format mapper functions and fix wrong implementation.

webrtc/sdk/objc/Framework/Classes/avfoundationformatmapper.h

 /*
  *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#include <set>
+
 #import <AVFoundation/AVFoundation.h>
 #import <Foundation/Foundation.h>
 
 #include "webrtc/media/base/videocapturer.h"
 
 namespace webrtc {
 // Mapping from AVCaptureDeviceFormat to cricket::VideoFormat for given input
 // device.
-extern std::set<cricket::VideoFormat> GetSupportedVideoFormatsForDevice(
+std::set<cricket::VideoFormat> GetSupportedVideoFormatsForDevice(
     AVCaptureDevice* device);
 
 // Sets device format for the provided capture device. Returns YES/NO depending
 // on success.
-extern bool SetFormatForCaptureDevice(AVCaptureDevice* device,
-                                      AVCaptureSession* session,
-                                      const cricket::VideoFormat& format);
+bool SetFormatForCaptureDevice(AVCaptureDevice* device,
+                               AVCaptureSession* session,
+                               const cricket::VideoFormat& format);
 }