app_shell: Allow getUserMedia to select a capture device by id

extensions/shell/browser/media_capture_util.h

 // 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.
 
 #ifndef EXTENSIONS_SHELL_BROWSER_MEDIA_CAPTURE_UTIL_H_
 #define EXTENSIONS_SHELL_BROWSER_MEDIA_CAPTURE_UTIL_H_
 
 #include "base/macros.h"
 #include "content/public/common/media_stream_request.h"
 
 namespace content {
 class WebContents;
 }
 
 namespace extensions {
 
 class Extension;
 
 namespace media_capture_util {
 
-// Grants access to the first available audio capture device (if requested) and
-// the first available video capture device (if requested). Usually used as a
-// helper for media capture ProcessMediaAccessRequest().
-void GrantMediaStreamRequestWithFirstDevice(
-    content::WebContents* web_contents,
-    const content::MediaStreamRequest& request,
-    const content::MediaResponseCallback& callback,
-    const Extension* extension);
+// Grants access to audio and video capture devices.
+// * If the caller requests specific device ids, grants access to those.
+// * If the caller does not request specific ids, grants access to the first
+//   available device.
+// Usually used as a helper for media capture ProcessMediaAccessRequest().
+void GrantMediaStreamRequest(content::WebContents* web_contents,
+                             const content::MediaStreamRequest& request,
+                             const content::MediaResponseCallback& callback,
+                             const Extension* extension);
 
 }  // namespace media_capture_util
 }  // namespace extensions
 
 #endif  // EXTENSIONS_SHELL_BROWSER_MEDIA_CAPTURE_UTIL_H_