[iOS] Fix incorrectly oriented frames when rapidly switching between cameras.

webrtc/sdk/objc/Framework/Classes/Video/RTCImageHelper.h

Index: webrtc/sdk/objc/Framework/Classes/Video/RTCImageHelper.h
diff --git a/webrtc/sdk/objc/Framework/Classes/Video/RTCImageHelper.h b/webrtc/sdk/objc/Framework/Classes/Video/RTCImageHelper.h
new file mode 100644
index 0000000000000000000000000000000000000000..44823c8e239ac59b7a4f6eed3c09b2d9403f14d4
--- /dev/null
+++ b/webrtc/sdk/objc/Framework/Classes/Video/RTCImageHelper.h
@@ -0,0 +1,23 @@
+/*
+ *  Copyright 2017 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.
+ */
+
+#import <AVFoundation/AVFoundation.h>
+#import <CoreMedia/CoreMedia.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface RTCImageHelper : NSObject

[tkchin_webrtc, 2017/07/24 23:16:54]

nit: consider putting this in to a category of AVCaptureSession e.g.
AVCaptureSession+DevicePosition

+
+// Check the image's EXIF for the actual camera the image came.
++ (AVCaptureDevicePosition)devicePositionForSampleBuffer:(CMSampleBufferRef)sampleBuffer;
+
+@end
+
+NS_ASSUME_NONNULL_END