(WIP) Use generator to generate externs for chrome.fileManagerPrivate API.

ui/file_manager/gallery/js/gallery.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.
 
 /**
  * Overrided metadata worker's path.
  * @type {string}
  */
 ContentMetadataProvider.WORKER_SCRIPT = '/js/metadata_worker.js';
 
@@ skipping 740 matching lines @@
  *
  * @param {!Event} event
  * @private
  */
 Gallery.prototype.onKeyDown_ = function(event) {
   var keyString = util.getKeyModifiers(event) + event.key;
 
   // Handle debug shortcut keys.
   switch (keyString) {
     case 'Ctrl-Shift-I': // Ctrl+Shift+I
-      chrome.fileManagerPrivate.openInspector('normal');
+      chrome.fileManagerPrivate.openInspector(
+          chrome.fileManagerPrivate.InspectionType.NORMAL);
       break;
     case 'Ctrl-Shift-J': // Ctrl+Shift+J
-      chrome.fileManagerPrivate.openInspector('console');
+      chrome.fileManagerPrivate.openInspector(
+          chrome.fileManagerPrivate.InspectionType.CONSOLE);
       break;
     case 'Ctrl-Shift-C': // Ctrl+Shift+C
-      chrome.fileManagerPrivate.openInspector('element');
+      chrome.fileManagerPrivate.openInspector(
+          chrome.fileManagerPrivate.InspectionType.ELEMENT);
       break;
     case 'Ctrl-Shift-B': // Ctrl+Shift+B
-      chrome.fileManagerPrivate.openInspector('background');
+      chrome.fileManagerPrivate.openInspector(
+          chrome.fileManagerPrivate.InspectionType.BACKGROUND);
       break;
   }
 
   // Do not capture keys when share dialog is shown.
   if (this.shareDialog_.isShowing())
     return;
 
   // Show UIs when user types any key.
   this.dimmableUIController_.kick();
 
@@ skipping 293 matching lines @@
  */
 var initializePromise =
     Promise.all([loadTimeDataPromise, volumeManagerPromise]).
     then(function(args) {
       var volumeManager = args[1];
       gallery = new Gallery(volumeManager);
     });
 
 // Loads entries.
 initializePromise.then(reload);