iOS: Fix rotation bug for back camera

webrtc/sdk/objc/Framework/Classes/avfoundationvideocapturer.mm

 /*
  *  Copyright 2015 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.
  */
 
@@ skipping 611 matching lines @@
 - (void)updateOrientation {
 #if TARGET_OS_IPHONE
   switch ([UIDevice currentDevice].orientation) {
     case UIDeviceOrientationPortrait:
       _rotation = webrtc::kVideoRotation_90;
       break;
     case UIDeviceOrientationPortraitUpsideDown:
       _rotation = webrtc::kVideoRotation_270;
       break;
     case UIDeviceOrientationLandscapeLeft:
-      _rotation = webrtc::kVideoRotation_180;
+      _rotation = _capturer->GetUseBackCamera() ? webrtc::kVideoRotation_0
+                                                : webrtc::kVideoRotation_180;
       break;
     case UIDeviceOrientationLandscapeRight:
-      _rotation = webrtc::kVideoRotation_0;
+      _rotation = _capturer->GetUseBackCamera() ? webrtc::kVideoRotation_180
+                                                : webrtc::kVideoRotation_0;
       break;
     case UIDeviceOrientationFaceUp:
     case UIDeviceOrientationFaceDown:
     case UIDeviceOrientationUnknown:
       // Ignore.
       break;
   }
 #endif
 }
 
@@ skipping 179 matching lines @@
       buffer = rotated_buffer;
     }
   }
 
   OnFrame(cricket::WebRtcVideoFrame(buffer, rotation,
                                     translated_camera_time_us, 0),
           captured_width, captured_height);
 }
 
 }  // namespace webrtc