PDFExtensionTest: Stop using chrome:// URL to load mock-interactions.js

chrome/test/data/pdf/test_util.js

 // Copyright 2015 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.
 
 // Utilities that are used in multiple tests.
 function MockWindow(width, height, sizer) {
   this.innerWidth = width;
   this.innerHeight = height;
   this.addEventListener = function(e, f) {
     if (e == 'scroll')
@@ skipping 86 matching lines @@
       width: w,
       height: h
     });
   };
   this.reset = function() {
     this.width = 0;
     this.height = 0;
     this.pageDimensions = [];
   };
 }
-
-function importHTML(src) {
-  var link = document.createElement('link');
-  var promise = new Promise(function(resolve, reject) {
-    link.onload = resolve;
-    link.onerror = reject;
-  });
-  link.rel = 'import';
-  link.href = src;
-  document.head.appendChild(link);
-  return promise;
-}
-
-/**
- * Import iron-test-helpers into the test document.
- * @example
- *   importTestHelpers().then(function() {
- *     chrome.test.runTests(...);
- *   })
- */
-function importTestHelpers() {
-  return importHTML('chrome://resources/polymer/v1_0/iron-test-helpers/' +
-      'iron-test-helpers.html');
-}