Revert of Removed duplicated JS hasVideoInputDeviceOnSystem() test helper

chrome/test/data/webrtc/media_devices.js

 /**
  * 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.
  */
 
 /**
  * Queries for media devices on the current system using the getMediaDevices
  * API.
  *
  * Returns the list of devices available.
  */
 function getMediaDevices() {
   navigator.getMediaDevices(function(devices) {
     returnToTest(JSON.stringify(devices));
   });
 }
 
 /**
  * Queries for media sources on the current system using the getSources API.
  *
  * Returns the list of sources available.
  */
 function getSources() {
   MediaStreamTrack.getSources(function(sources) {
     returnToTest(JSON.stringify(sources));
   });
 }
 
+/**
+ * Queries for video input devices on the current system using the
+ * getSources API.
+ *
+ * This does not guarantee that a getUserMedia with video will succeed, as the
+ * camera could be busy for instance.
+ *
+ * Returns has-video-input-device to the test if there is a webcam available,
+ * no-video-input-devices otherwise.
+ */
+function hasVideoInputDeviceOnSystem() {
+  MediaStreamTrack.getSources(function(devices) {
+    var hasVideoInputDevice = false;
+    devices.forEach(function(device) {
+      if (device.kind == 'video')
+        hasVideoInputDevice = true;
+    });
+
+    if (hasVideoInputDevice)
+      returnToTest('has-video-input-device');
+    else
+      returnToTest('no-video-input-devices');
+  });
+}