[Mojo Video Capture] Introduce abstraction VideoCaptureSystem

media/capture/video/video_capture_system.h

+// Copyright 2014 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_
+
+#include "media/capture/video/video_capture_device_factory.h"
+#include "media/capture/video/video_capture_device_info.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 {
+ public:
+  VideoCaptureSystem(std::unique_ptr<VideoCaptureDeviceFactory> factory);

[miu, 2017/03/22 22:51:24]

explicit

[chfremer, 2017/03/23 00:34:13]

Done.

+  ~VideoCaptureSystem();
+
+  void GetDeviceInfosAsync(
+      const base::Callback<void(const std::vector<VideoCaptureDeviceInfo>&)>&

[miu, 2017/03/22 22:51:23]

nit: Since the callback is used in more than one place, I'd suggest:

  using DeviceInfoCallback = base::Callback<void(const
std::vector<VideoCaptureDeviceInfo>&)>;
  void GetDeviceInfosAsync(const DeviceInfoCallback& result_callback);

[chfremer, 2017/03/23 00:34:13]

Done.

+          result_callback);
+
+  // Creates a VideoCaptureDevice object. Returns NULL if something goes wrong.
+  std::unique_ptr<VideoCaptureDevice> CreateDevice(const std::string device_id);
+
+  media::VideoCaptureDeviceFactory* video_capture_device_factory() {

[miu, 2017/03/22 22:51:24]

nit:

  media::VideoCaptureDeviceFactory* video_capture_device_factory() const {
                                                                   ^^^^^

[miu, 2017/03/22 22:51:24]

Is the plan to remove this accessor in later CLs, and just do everything via
VideoCaptureSystem?

[chfremer, 2017/03/23 00:34:13]

Done.

[chfremer, 2017/03/23 00:34:13]

Yes. This accessor is going to go away in CL19.

+    return factory_.get();
+  }
+
+ private:
+  void OnDescriptorsReceived(
+      const base::Callback<void(const std::vector<VideoCaptureDeviceInfo>&)>&

[miu, 2017/03/22 22:51:24]

DeviceInfoCallback here. (and in the methods in the .cc file)

[chfremer, 2017/03/23 00:34:14]

Done.

+          result_callback,
+      std::unique_ptr<VideoCaptureDeviceDescriptors> descriptors);
+
+  // Returns false if no descriptor found.
+  bool LookupDescriptorFromId(const std::string& device_id,
+                              media::VideoCaptureDeviceDescriptor* descriptor);
+
+  const std::unique_ptr<VideoCaptureDeviceFactory> factory_;
+  std::vector<VideoCaptureDeviceInfo> devices_info_cache_;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_CAPTURE_VIDEO_VIDEO_CAPTURE_DEVICE_FACTORY_H_