media: add video capture device for ARC++ camera HAL v3

media/capture/video/chromeos/video_capture_device_factory_chromeos.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_CHROMEOS_VIDEO_CAPTURE_DEVICE_FACTORY_CHROMEOS_H_
+#define MEDIA_CAPTURE_VIDEO_CHROMEOS_VIDEO_CAPTURE_DEVICE_FACTORY_CHROMEOS_H_
+
+#include <memory>
+
+#include "base/macros.h"
+#include "media/capture/video/chromeos/camera_hal_delegate.h"
+#include "media/capture/video/video_capture_device_factory.h"
+
+namespace media {
+
+class CAPTURE_EXPORT VideoCaptureDeviceFactoryChromeOS final
+    : public VideoCaptureDeviceFactory {
+ public:
+  VideoCaptureDeviceFactoryChromeOS(

[wuchengli, 2017/04/28 06:29:28]

explicit

[jcliang, 2017/04/28 08:27:49]

Done.

+      scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner);
+
+  ~VideoCaptureDeviceFactoryChromeOS();
+
+  // VideoCaptureDeviceFactory interface implementations.
+  std::unique_ptr<VideoCaptureDevice> CreateDevice(
+      const VideoCaptureDeviceDescriptor& device_descriptor) final;
+  void GetSupportedFormats(
+      const VideoCaptureDeviceDescriptor& device_descriptor,
+      VideoCaptureFormats* supported_formats) final;
+  void GetDeviceDescriptors(
+      VideoCaptureDeviceDescriptors* device_descriptors) final;
+
+  // Initializes the factory. The factory is functional only after this call
+  // succeeds.  This method is called on the browser IO thread when the factory

[wuchengli, 2017/04/28 06:29:28]

Check why this is on IO thread. From the code, this seems to be on UI thread.

[jcliang, 2017/04/28 08:27:49]

I just verified this by manually inserting logs in this function. It's called on
UI thread.

The comment here says the factory is created on IO thread:
https://cs.chromium.org/chromium/src/media/capture/video/video_capture_device...,
so it's probably outdated.

[chfremer, 2017/04/28 16:57:18]

That is my bad. I changed this threading in a recent CL [1] but failed to find
and change the comment.
Could you do me a favor and update the comment?

[1] https://codereview.chromium.org/2787703004/

[jcliang, 2017/04/29 06:55:38]

Uploaded another CL for the fix: https://codereview.chromium.org/2849023002

+  // instance is created.
+  bool Init();
+
+ private:
+  const scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
+
+  // The thread that all the Mojo operations of |camera_hal_delegate_| take
+  // place.  Started in Init and stopped when the class instance is destroyed.

[wuchengli, 2017/04/28 06:29:28]

Can we make Start and Stop run on the same thread? base::Thread has a
commented-out DCHECK.

[jcliang, 2017/04/28 08:27:49]

The thread is started on UI thread when the browser mainloop bootstraps. The
factory instance is a singleton in the browser process, so in theory it's never
stopped.

+  base::Thread module_thread_;
+
+  // Communication interface to the camera HAL. |camera_hal_delegate_| is
+  // created on the thread where the VideoCaptureDeviceFactoryChromeOS was
+  // instantiated. All the Mojo communication that |camera_hal_delegate_|
+  // issues and receives must be sequenced through |module_thread_|.
+  scoped_refptr<CameraHalDelegate> camera_hal_delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(VideoCaptureDeviceFactoryChromeOS);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_CAPTURE_VIDEO_CHROMEOS_VIDEO_CAPTURE_DEVICE_FACTORY_CHROMEOS_H_