[Mojo Video Capture] Introduce abstraction BuildableVideoCaptureDevice

content/browser/renderer_host/media/video_capture_device_entry.h

+// Copyright 2016 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 CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_DEVICE_ENTRY_H_
+#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_DEVICE_ENTRY_H_
+
+#include "content/browser/renderer_host/media/buildable_video_capture_device.h"
+#include "content/browser/renderer_host/media/video_capture_controller.h"
+#include "content/public/common/media_stream_request.h"
+
+namespace content {
+
+// When first created (in GetOrCreateDeviceEntry()), this consists of

[miu, 2017/03/11 01:13:22]

Is GetOrCreateDeviceEntry() in another class? Perhaps you could update the
class-level comments in terms of what owns instances of this and how it uses
this.

[chfremer, 2017/03/13 22:02:03]

Thanks for pointing this out. I removed the "(in GetOrCreateDeviceEntry())" part
of the comment, since this class is no longer inside the scope of
VideoCaptureManager.

I generally try to avoid using the class-level comment to explain where a class
is used. Doing so would encourage tight coupling between the class and its
users. To look up usages of the class, we can instead safely use the code search
tool.

+// only the |controller_|. Clients can already connect to the controller, but
+// there is no |video_capture_device| present. A call to
+// CreateAndStartDeviceAsync() asynchronously brings up the given
+// |buildable_device| and connects it to the controller. If
+// CreateAndStartDeviceAsync() has beend called, ReleaseDeviceAsync() must be
+// called before releasing the instance.
+// Instances must be RefCountedThreadSafe, because an owner
+// (VideoCaptureManager) wants to be able to release its reference during an
+// (asynchronously executing) run of CreateAndStartDeviceAsync(). To this end,
+// the owner passes in the shared ownership as part of |context_reference| into
+// CreateAndStartDeviceAsync().
+class VideoCaptureDeviceEntry
+    : public base::RefCountedThreadSafe<VideoCaptureDeviceEntry> {
+ public:
+  VideoCaptureDeviceEntry(
+      const std::string& id,
+      MediaStreamType stream_type,
+      const media::VideoCaptureParams& params,
+      std::unique_ptr<BuildableVideoCaptureDevice> buildable_device);
+
+  // The passed-in |context_reference| must guarantee that the context relevant
+  // during the asynchronous processing stays alive.
+  void CreateAndStartDeviceAsync(const media::VideoCaptureParams& params,
+                                 BuildableDeviceCallbacks* callbacks,
+                                 std::unique_ptr<Ownership> context_reference);
+  // The passed-in |context_reference| must guarantee that the context relevant
+  // during the asynchronous processing stays alive.
+  void ReleaseDeviceAsync(std::unique_ptr<Ownership> context_reference);
+
+  void OnLog(const std::string& message);
+  void OnError();
+  bool HasDevice() const;
+  bool CorrespondsToController(const VideoCaptureController* controller) const;
+  bool HasActiveClient();
+  bool HasPausedClient();
+  void AddClient(VideoCaptureControllerID id,
+                 VideoCaptureControllerEventHandler* event_handler,
+                 media::VideoCaptureSessionId session_id,
+                 const media::VideoCaptureParams& params);
+  // Ends a client's session "involuntarily", meaning the session is stopped
+  // without the client requesting it.
+  void StopSession(int session_id);
+  base::WeakPtr<VideoCaptureController> GetControllerWeakPtrForIOThread();
+  media::VideoCaptureFormat GetVideoCaptureFormat();
+
+  void GetPhotoCapabilities(
+      media::VideoCaptureDevice::GetPhotoCapabilitiesCallback callback) const;
+  void SetPhotoOptions(
+      media::mojom::PhotoSettingsPtr settings,
+      media::VideoCaptureDevice::SetPhotoOptionsCallback callback);
+  void TakePhoto(media::VideoCaptureDevice::TakePhotoCallback callback);
+  void MaybeSuspend();
+  void Resume();
+  void RequestRefreshFrame();
+
+  // The passed-in |context_reference| must guarantee that the context relevant
+  // during the asynchronous processing stays alive.
+  void SetDesktopCaptureWindowIdAsync(
+      gfx::NativeViewId window_id,
+      std::unique_ptr<Ownership> context_reference);
+
+  int serial_id() const { return serial_id_; }
+  const std::string& id() const { return id_; }
+  MediaStreamType stream_type() const { return stream_type_; }
+  const media::VideoCaptureParams& parameters() const { return parameters_; }
+
+ private:
+  friend class base::RefCountedThreadSafe<VideoCaptureDeviceEntry>;
+  virtual ~VideoCaptureDeviceEntry();
+
+  const int serial_id_;
+  const std::string id_;
+  const MediaStreamType stream_type_;
+  const media::VideoCaptureParams parameters_;
+  std::unique_ptr<BuildableVideoCaptureDevice> buildable_device_;
+  VideoCaptureController controller_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_DEVICE_ENTRY_H_