[Mojo Video Capture] Hook up video capture service behind a feature flag

content/browser/renderer_host/media/video_capture_provider_switcher.h

+// Copyright 2016 The Chromium Authors. All rights reserved.

[mcasas, 2017/05/10 02:33:33]

s/2016/2017/

[chfremer, 2017/05/10 17:59:39]

Done.

+// 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_PROVIDER_SWITCHER_H_
+#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_PROVIDER_SWITCHER_H_
+
+#include "content/browser/renderer_host/media/video_capture_provider.h"
+#include "services/video_capture/public/interfaces/device_factory.mojom.h"
+
+namespace content {
+
+// Routes requests for media devices, e.g. cameras, to
+// |media_device_capture_provider| and for all other types of capture, e.g.
+// screen or tab capture, to the given |other_types_capture_provider|.
+class CONTENT_EXPORT VideoCaptureProviderSwitcher
+    : public VideoCaptureProvider {
+ public:
+  VideoCaptureProviderSwitcher(
+      std::unique_ptr<VideoCaptureProvider> media_device_capture_provider,
+      std::unique_ptr<VideoCaptureProvider> other_types_capture_provider);
+  ~VideoCaptureProviderSwitcher() override;
+
+  void Uninitialize() override;
+
+  void GetDeviceInfosAsync(
+      const base::Callback<void(
+          const std::vector<media::VideoCaptureDeviceInfo>&)>& result_callback)
+      override;
+
+  std::unique_ptr<VideoCaptureDeviceLauncher> CreateDeviceLauncher() override;
+
+ private:
+  std::unique_ptr<VideoCaptureProvider> media_device_capture_provider_;
+  std::unique_ptr<VideoCaptureProvider> other_types_capture_provider_;
+};
+
+class CONTENT_EXPORT VideoCaptureDeviceLauncherSwitcher

[mcasas, 2017/05/10 02:33:33]

I'm not sure about having two classes bound together, have
you found more examples of such construction in //content ?

[chfremer, 2017/05/10 17:59:39]

What is your concern about this type of construction?
To me it appears to be a clean solution to a valid need.

[mcasas, 2017/05/10 18:15:44]

My concern is what I wrote: "having two classes bound 
together" in the same file.  Examples?

[chfremer, 2017/05/10 21:08:05]

Ah, two classes in the same file. 
Yes that is indeed uncommon in //content.
Since VideoCaptureDeviceLauncherSwitcher is only ever created by
VideoCaptureProviderSwitcher, I now moved it into its cc-file-scope.

Done.

+    : public VideoCaptureDeviceLauncher {
+ public:
+  VideoCaptureDeviceLauncherSwitcher(
+      std::unique_ptr<VideoCaptureDeviceLauncher> media_device_launcher,
+      std::unique_ptr<VideoCaptureDeviceLauncher> other_types_launcher);
+  ~VideoCaptureDeviceLauncherSwitcher() override;
+
+  void LaunchDeviceAsync(const std::string& device_id,
+                         MediaStreamType stream_type,
+                         const media::VideoCaptureParams& params,
+                         base::WeakPtr<media::VideoFrameReceiver> receiver,
+                         Callbacks* callbacks,
+                         base::OnceClosure done_cb) override;
+
+  void AbortLaunch() override;
+
+ private:
+  std::unique_ptr<VideoCaptureDeviceLauncher> media_device_launcher_;
+  std::unique_ptr<VideoCaptureDeviceLauncher> other_types_launcher_;
+  base::Optional<MediaStreamType> last_launched_stream_type_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_PROVIDER_SWITCHER_H_