Add a data source field for volumes.

chrome/test/data/extensions/api_test/file_system_provider/mount/test.js

 // Copyright 2013 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.
 
 'use strict';
 
 /**
  * Runs all of the test cases, one by one.
  */
 chrome.test.runTests([
@@ skipping 47 matching lines @@
       openedFilesLimit: -1
     }, chrome.test.callbackFail('INVALID_OPERATION'));
   },
 
   // End to end test. Mounts a volume using fileSystemProvider.mount(), then
   // checks if the mounted volume is added to VolumeManager, by querying
   // fileManagerPrivate.getVolumeMetadataList().
   function successfulMount() {
     var fileSystemId = 'caramel-candy';
     chrome.fileSystemProvider.mount(
-        {fileSystemId: fileSystemId, displayName: 'caramel-candy.zip'},
+        {
+          fileSystemId: fileSystemId,
+          displayName: 'caramel-candy.zip',
+          source: 'FILE'
+        },
         chrome.test.callbackPass(function() {
           chrome.fileManagerPrivate.getVolumeMetadataList(function(volumeList) {
             var volumeInfo;
             volumeList.forEach(function(inVolumeInfo) {
               if (inVolumeInfo.extensionId == chrome.runtime.id &&
                   inVolumeInfo.fileSystemId == fileSystemId) {
                 volumeInfo = inVolumeInfo;
               }
             });
             chrome.test.assertTrue(!!volumeInfo);
@@ skipping 47 matching lines @@
             {
               fileSystemId: 'over-the-limit-fs-id',
               displayName: 'Over The Limit File System'
             },
             chrome.test.callbackFail('TOO_MANY_OPENED'));
       }
     };
     tryNextOne();
   }
 ]);