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"
+
+using content::MediaCaptureDevices;
+using content::MediaStreamDevices;
+using content::MediaStreamUI;
+
+namespace extensions {
+namespace media_capture_util {
+
+// See also Chrome's MediaCaptureDevicesDispatcher.

[James Cook, 2014/08/20 18:17:16]

I looked at refactoring MediaCaptureDevicesDispatcher but it's tied to Chrome UI
concepts, tab/screen capture, injection of test devices, etc.  In theory some of
it could be pushed down into src/content and some pulled here, but I think it
would make all the pieces harder to understand.

+void GrantMediaStreamRequestWithFirstDevice(
+    content::WebContents* web_contents,
+    const content::MediaStreamRequest& request,
+    const content::MediaResponseCallback& callback) {
+  // 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;
+
+  if (request.audio_type == content::MEDIA_DEVICE_AUDIO_CAPTURE) {
+    // Use first available audio capture device.
+    const MediaStreamDevices& audio_devices =
+        MediaCaptureDevices::GetInstance()->GetAudioCaptureDevices();
+    if (!audio_devices.empty())
+      devices.push_back(audio_devices[0]);
+  }
+
+  if (request.video_type == content::MEDIA_DEVICE_VIDEO_CAPTURE) {
+    // Use first available video capture device.
+    const MediaStreamDevices& video_devices =
+        MediaCaptureDevices::GetInstance()->GetVideoCaptureDevices();
+    if (!video_devices.empty())
+      devices.push_back(video_devices[0]);
+  }
+
+  // Don't show UI.
+  scoped_ptr<MediaStreamUI> ui;
+  callback.Run(devices,
+               devices.empty() ? content::MEDIA_DEVICE_INVALID_STATE
+                               : content::MEDIA_DEVICE_OK,
+               ui.Pass());
+}
+
+}  // namespace media_capture_util
+}  // namespace extensions