Reland of rotate frames correctly for back camera

media/capture/video/linux/video_capture_device_linux.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Linux specific implementation of VideoCaptureDevice.
 // V4L2 is used for capturing. V4L2 does not provide its own thread for
 // capturing so this implementation uses a Chromium thread for fetching frames
 // from V4L2.
 
 #ifndef MEDIA_CAPTURE_VIDEO_LINUX_VIDEO_CAPTURE_DEVICE_LINUX_H_
@@ skipping 27 matching lines @@
   // VideoCaptureDevice implementation.
   void AllocateAndStart(const VideoCaptureParams& params,
                         std::unique_ptr<Client> client) override;
   void StopAndDeAllocate() override;
   void TakePhoto(TakePhotoCallback callback) override;
   void GetPhotoCapabilities(GetPhotoCapabilitiesCallback callback) override;
   void SetPhotoOptions(mojom::PhotoSettingsPtr settings,
                        SetPhotoOptionsCallback callback) override;
 
  protected:
-  void SetRotation(int rotation);
+  virtual void SetRotation(int rotation);
+
+  const VideoCaptureDeviceDescriptor device_descriptor_;
 
  private:
   static int TranslatePowerLineFrequencyToV4L2(PowerLineFrequency frequency);
 
   // Internal delegate doing the actual capture setting, buffer allocation and
   // circulation with the V4L2 API. Created and deleted in the thread where
   // VideoCaptureDeviceLinux lives but otherwise operating on |v4l2_thread_|.
   scoped_refptr<V4L2CaptureDelegate> capture_impl_;
 
   base::Thread v4l2_thread_;  // Thread used for reading data from the device.
 
-  const VideoCaptureDeviceDescriptor device_descriptor_;
-
   DISALLOW_IMPLICIT_CONSTRUCTORS(VideoCaptureDeviceLinux);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_CAPTURE_VIDEO_LINUX_VIDEO_CAPTURE_DEVICE_LINUX_H_