Avoid cross-origin iframe issues when loading PDF in print preview

chrome/browser/resources/pdf/pdf_scripting_api.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.
 
 /**
  * Turn a dictionary received from postMessage into a key event.
  * @param {Object} dict A dictionary representing the key event.
  * @return {Event} A key event.
  */
 function DeserializeKeyEvent(dict) {
@@ skipping 38 matching lines @@
  * the PDF viewer so that it can be customized by things like print preview.
  * @param {Window} window the window of the page containing the pdf viewer.
  * @param {Object} plugin the plugin element containing the pdf viewer.
  */
 function PDFScriptingAPI(window, plugin) {
   this.loadState_ = LoadState.LOADING;
   this.pendingScriptingMessages_ = [];
   this.setPlugin(plugin);
 
   window.addEventListener('message', function(event) {
-    if (event.origin != 'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai') {
+    if (event.origin != 'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai' &&
+        event.origin != 'chrome://print') {
       console.error('Received message that was not from the extension: ' +
                     event);
       return;
     }
     switch (event.data.type) {
       case 'viewport':
         if (this.viewportChangedCallback_)
           this.viewportChangedCallback_(event.data.pageX,
                                         event.data.pageY,
                                         event.data.pageWidth,
@@ skipping 194 matching lines @@
  * Creates a PDF viewer with a scripting interface. This is basically 1) an
  * iframe which is navigated to the PDF viewer extension and 2) a scripting
  * interface which provides access to various features of the viewer for use
  * by print preview and accessibility.
  * @param {string} src the source URL of the PDF to load initially.
  * @return {HTMLIFrameElement} the iframe element containing the PDF viewer.
  */
 function PDFCreateOutOfProcessPlugin(src) {
   var client = new PDFScriptingAPI(window);
   var iframe = window.document.createElement('iframe');
+  iframe.setAttribute('src', 'pdf_preview.html?' + src);
   // Prevent the frame from being tab-focusable.
   iframe.setAttribute('tabindex', '-1');
 
-  var EXTENSION_URL =
-      'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai/index.html';
-  iframe.setAttribute('src', EXTENSION_URL + '?' + src);
   iframe.onload = function() {
     client.setPlugin(iframe.contentWindow);
   };
 
   // Add the functions to the iframe so that they can be called directly.
   iframe.setViewportChangedCallback =
       client.setViewportChangedCallback.bind(client);
   iframe.setLoadCallback = client.setLoadCallback.bind(client);
   iframe.setKeyEventCallback = client.setKeyEventCallback.bind(client);
   iframe.resetPrintPreviewMode = client.resetPrintPreviewMode.bind(client);
   iframe.loadPreviewPage = client.loadPreviewPage.bind(client);
   iframe.sendKeyEvent = client.sendKeyEvent.bind(client);
   return iframe;
 }