Change the print preview UI to use the material design style buttons for zoom

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 251 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',
-      'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai/index.html?' + src);
   // Prevent the frame from being tab-focusable.
   iframe.setAttribute('tabindex', '-1');
-  var client = new PDFScriptingAPI(window);
-  iframe.onload = function() {
-    client.setPlugin(iframe.contentWindow);
-  };
+
+  // TODO(raymes): This below is a hack to tell if the material design PDF UI
+  // has been enabled. Remove this as soon as we remove the material design PDF
+  // flag.
+  var EXTENSION_URL = 'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai/';
+  var PAGE_NAME = 'index.html';
+  var MATERIAL_PAGE_NAME = 'index-material.html';
+  fetch(EXTENSION_URL + PAGE_NAME, {
+    method: 'get'
+  }).then(function() {
+    iframe.setAttribute('src', EXTENSION_URL + PAGE_NAME + '?' + src);
+  }, function() {
+    iframe.setAttribute('src', EXTENSION_URL + MATERIAL_PAGE_NAME + '?' + src);
+  }).then(function() {
+    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;
 }