Add browser test to the sharing dialog feature in Files.app.

chrome/browser/resources/file_manager/js/background.js

 // Copyright (c) 2012 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';
 
 /**
  * Map of all currently open app window. The key is an app id.
  */
 var appWindows = {};
@@ skipping 122 matching lines @@
       // Show after changing bounds is done. For the new UI, Files.app shows
       // it's window as soon as the UI is pre-initialized.
       if (!this.id_.match(FILES_ID_PATTERN))
         appWindow.show();
 
       appWindows[this.id_] = appWindow;
       var contentWindow = appWindow.contentWindow;
       contentWindow.appID = this.id_;
       contentWindow.appState = this.appState_;
       contentWindow.appInitialURL = this.url_;
+      if (window.IN_TEST)
+        contentWindow.IN_TEST = true;
       appWindow.onClosed.addListener(function() {
         if (contentWindow.unload)
           contentWindow.unload();
         if (contentWindow.saveOnExit) {
           contentWindow.saveOnExit.forEach(function(entry) {
             util.AppCache.update(entry.key, entry.value);
           });
         }
         delete appWindows[this.id_];
         chrome.storage.local.remove(this.id_);  // Forget the persisted state.
@@ skipping 415 matching lines @@
   queue.run(function(callback) {
     chrome.fileBrowserPrivate.getStrings(function(strings) {
       initContextMenu(strings);
       chrome.storage.local.set({strings: strings}, callback);
     });
   });
 }
 
 // Initialize Files.app.
 initApp();