app_shell: Add audio and video capture support

extensions/shell/browser/media_capture_util.cc

+// 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.
+
+#include "extensions/shell/browser/media_capture_util.h"
+
+#include "base/callback.h"
+#include "base/logging.h"
+#include "content/public/browser/media_capture_devices.h"
+#include "extensions/common/permissions/permissions_data.h"
+using content::MediaCaptureDevices;

[no longer working on chromium, 2014/08/22 19:22:27]

nit, add an empty line before using content::MediaCaptureDevices;

[James Cook, 2014/08/22 20:11:00]

Oops, done.

+using content::MediaStreamDevices;
+using content::MediaStreamUI;
+
+namespace extensions {
+namespace media_capture_util {
+
+// See also Chrome's MediaCaptureDevicesDispatcher.
+void GrantMediaStreamRequestWithFirstDevice(
+    content::WebContents* web_contents,
+    const content::MediaStreamRequest& request,
+    const content::MediaResponseCallback& callback,
+    const Extension* extension) {
+  // app_shell only supports audio and video capture, not tab or screen capture.
+  DCHECK(request.audio_type == content::MEDIA_DEVICE_AUDIO_CAPTURE ||
+         request.video_type == content::MEDIA_DEVICE_VIDEO_CAPTURE);
+
+  // app_shell does not support requesting a specific device ID.
+  DCHECK(request.requested_audio_device_id.empty() &&
+         request.requested_video_device_id.empty());
+
+  MediaStreamDevices devices;
+  const PermissionsData* permissions_data = extension->permissions_data();
+
+  if (request.audio_type == content::MEDIA_DEVICE_AUDIO_CAPTURE) {
+    if (permissions_data->HasAPIPermission(APIPermission::kAudioCapture)) {

[no longer working on chromium, 2014/08/22 19:22:26]

If I understand your comment correctly, app_shell only runs trusted apps, that
says the trust apps should only call this method if they have permission, if so,
should we add a CHECK here instead?

[James Cook, 2014/08/22 20:11:00]

Yes, I think a CHECK here is better. Done.

+      const MediaStreamDevices& audio_devices =
+          MediaCaptureDevices::GetInstance()->GetAudioCaptureDevices();
+      // Use first available audio capture device.
+      if (!audio_devices.empty())
+        devices.push_back(audio_devices[0]);
+    } else {
+      // app_shell has no UI surface to show the error, so log it.
+      LOG(WARNING) << "Audio capture request but no audioCapture permission.";
+    }
+  }
+
+  if (request.video_type == content::MEDIA_DEVICE_VIDEO_CAPTURE) {
+    if (permissions_data->HasAPIPermission(APIPermission::kVideoCapture)) {
+      const MediaStreamDevices& video_devices =
+          MediaCaptureDevices::GetInstance()->GetVideoCaptureDevices();
+      // Use first available video capture device.
+      if (!video_devices.empty())
+        devices.push_back(video_devices[0]);
+    } else {
+      // app_shell has no UI surface to show the error, so log it.
+      LOG(WARNING) << "Video capture request but no videoCapture permission.";
+    }
+  }
+
+  // Don't show UI.
+  scoped_ptr<MediaStreamUI> ui;
+  callback.Run(devices,

[no longer working on chromium, 2014/08/22 19:22:26]

Just FTR, for a website, Chrome will show some notification UIs (a red favicon
and a camera icon on the right of URL ) to notify the users that the website is
doing recording, even though the website has permission (considered to be
trusted in some way).

I do understand that things might be different for an app, but just wondering if
we should somehow notify the users that the recording is ongoing, or is it
possible at all?

[James Cook, 2014/08/22 20:11:00]

Yeah, unfortunately we don't have a good UI surface for an indicator. Packaged
apps don't have a URL bar.  On desktop we show an icon in the system tray, but
app_shell apps are fullscreen.

Fortunately for the internal project we're considering the camera will have a
physical "recording" light. For other apps I think we have to rely on the app
author so show a recording indicator.

Added a TODO here -- I don't have a good solution.

+               devices.empty() ? content::MEDIA_DEVICE_INVALID_STATE
+                               : content::MEDIA_DEVICE_OK,
+               ui.Pass());
+}
+
+}  // namespace media_capture_util
+}  // namespace extensions