[Mojo Video Capture] Fix VideoCaptureManager exposing implementation details to clients

media/capture/video/video_capture_system_impl.h

 // Copyright 2017 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.
 
-#ifndef MEDIA_CAPTURE_VIDEO_VIDEO_CAPTURE_SYSTEM_H_
-#define MEDIA_CAPTURE_VIDEO_VIDEO_CAPTURE_SYSTEM_H_
+#ifndef MEDIA_CAPTURE_VIDEO_VIDEO_CAPTURE_SYSTEM_IMPL_H_
+#define MEDIA_CAPTURE_VIDEO_VIDEO_CAPTURE_SYSTEM_IMPL_H_
 
-#include "media/capture/video/video_capture_device_factory.h"
-#include "media/capture/video/video_capture_device_info.h"
+#include "media/capture/video/video_capture_system.h"
 
 namespace media {
 
 // Layer on top of VideoCaptureDeviceFactory that translates device descriptors
 // to string identifiers and consolidates and caches device descriptors and
 // supported formats into VideoCaptureDeviceInfos.
-class CAPTURE_EXPORT VideoCaptureSystem {
+class CAPTURE_EXPORT VideoCaptureSystemImpl : public VideoCaptureSystem {
  public:
-  using DeviceInfoCallback =
-      base::Callback<void(const std::vector<VideoCaptureDeviceInfo>&)>;
+  explicit VideoCaptureSystemImpl(
+      std::unique_ptr<VideoCaptureDeviceFactory> factory);
+  ~VideoCaptureSystemImpl() override;
 
-  explicit VideoCaptureSystem(
-      std::unique_ptr<VideoCaptureDeviceFactory> factory);
-  ~VideoCaptureSystem();
-
-  // The passed-in |result_callback| must have ownership of the called
-  // VideoCaptureSystem instance to guarantee that it stays alive during the
-  // asynchronous operation.
-  void GetDeviceInfosAsync(const DeviceInfoCallback& result_callback);
-
-  // Creates a VideoCaptureDevice object. Returns nullptr if something goes
-  // wrong.
+  void GetDeviceInfosAsync(const DeviceInfoCallback& result_callback) override;
   std::unique_ptr<VideoCaptureDevice> CreateDevice(
-      const std::string& device_id);
-
-  media::VideoCaptureDeviceFactory* video_capture_device_factory() const {
-    return factory_.get();
-  }
+      const std::string& device_id) override;
 
  private:
   void OnDescriptorsReceived(
       const DeviceInfoCallback& result_callback,
       std::unique_ptr<VideoCaptureDeviceDescriptors> descriptors);
 
   // Returns nullptr if no descriptor found.
   const VideoCaptureDeviceInfo* LookupDeviceInfoFromId(
       const std::string& device_id);
 
   const std::unique_ptr<VideoCaptureDeviceFactory> factory_;
   std::vector<VideoCaptureDeviceInfo> devices_info_cache_;
 
   base::ThreadChecker thread_checker_;
 };
 
 }  // namespace media
 
-#endif  // MEDIA_CAPTURE_VIDEO_VIDEO_CAPTURE_DEVICE_FACTORY_H_
+#endif  // MEDIA_CAPTURE_VIDEO_VIDEO_CAPTURE_SYSTEM_IMPL_H_