Initially load new_tab.css with a timestamp for chrome://apps.

chrome/browser/resources/ntp4/new_tab.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.
 
 /**
  * @fileoverview New tab page 4
  * This is the main code for a previous version of the Chrome NTP ("NTP4").
  * Some parts of this are still used for the chrome://apps page.
  */
 
@@ skipping 72 matching lines @@
       sectionsToWaitFor++;
       if (loadTimeData.getBoolean('showAppLauncherPromo')) {
         $('app-launcher-promo-close-button').addEventListener('click',
             function() { chrome.send('stopShowingAppLauncherPromo'); });
         $('apps-promo-learn-more').addEventListener('click',
             function() { chrome.send('onLearnMore'); });
       }
     }
     measureNavDots();
 
-    // Load the current theme colors.
-    themeChanged();
-
     newTabView = new NewTabView();
 
     if (!loadTimeData.getBoolean('showWebStoreIcon')) {
       var webStoreIcon = $('chrome-web-store-link');
       // Not all versions of the NTP have a footer, so this may not exist.
       if (webStoreIcon)
         webStoreIcon.hidden = true;
     } else {
       var webStoreLink = loadTimeData.getString('webStoreLink');
       var url = appendParam(webStoreLink, 'utm_source', 'chrome-ntp-launcher');
@@ skipping 330 matching lines @@
     setAppToBeHighlighted: setAppToBeHighlighted,
     setBookmarkBarAttached: setBookmarkBarAttached,
     themeChanged: themeChanged,
     updateLogin: updateLogin
   };
 });
 
 document.addEventListener('DOMContentLoaded', ntp.onLoad);
 
 var toCssPx = cr.ui.toCssPx;