Add browser test for VOLUME_TYPE_MTP volumes on Files.app.

chrome/test/data/extensions/api_test/file_manager_browsertest/background.js

 // Copyright (c) 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.
 
 'use strict';
 
 /**
  * Extension ID of Files.app.
  * @type {string}
  * @const
@@ skipping 600 matching lines @@
   ENTRIES.testSharedDocument
 ];
 
 var NESTED_ENTRY_SET = [
   ENTRIES.directoryA,
   ENTRIES.directoryB,
   ENTRIES.directoryC
 ];
 
 /**
+ * Expecetd list of preset entries in fake test volumes. This should be in sync
+ * with FakeTestVolume::PrepareTestEntries in the test harness.
+ *
+ * @type {Array.<TestEntryInfo>}
+ * @const
+ */
+var BASIC_FAKE_ENTRY_SET = [
+  ENTRIES.hello,
+  ENTRIES.directoryA
+];
+
+/**
  * Expected files shown in "Recent". Directories (e.g. 'photos') are not in this
  * list as they are not expected in "Recent".
  *
  * @type {Array.<TestEntryInfo>}
  * @const
  */
 var RECENT_ENTRY_SET = [
   ENTRIES.hello,
   ENTRIES.world,
   ENTRIES.desktop,
@@ skipping 174 matching lines @@
         chrome.test.fail(testCaseName + ' is not found.');
         return;
       }
       // Specify the name of test to the test system.
       targetTest.generatedName = testCaseName;
       chrome.test.runTests([targetTest]);
     }
   ];
   steps.shift()();
 });