Implement sendKeyEvent print preview function for OOP PDF.

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.
 
 /**
  * Create a new PDFScriptingAPI. This provides a scripting interface to
  * 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 {string} extensionUrl the url of the PDF extension.
  */
@@ skipping 131 matching lines @@
       message.page = page;
     this.sendMessage_(message);
     return true;
   },
 
   /**
    * Send a key event to the extension.
    * @param {number} keyCode the key code to send to the extension.
    */
   sendKeyEvent: function(keyCode) {
-    // TODO(raymes): Figure out a way to do this. It's only used to do scrolling
-    // the viewport, so probably just expose viewport controls instead.
+    this.sendMessage_({
+      type: 'sendKeyEvent',
+      keyCode: keyCode
+    });
   },
 };
 
 /**
  * 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 accessbility.
  * @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 EXTENSION_URL = 'chrome-extension://mhjfbmdgcfjbbpaeojofohoefgiehjai';
   var iframe = window.document.createElement('iframe');
   iframe.setAttribute('src', EXTENSION_URL + '/index.html?' + src);
   var client = new PDFScriptingAPI(window, EXTENSION_URL);
 
   // 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.resetPrintPreviewMode = client.resetPrintPreviewMode.bind(client);
   iframe.loadPreviewPage = client.loadPreviewPage.bind(client);
   iframe.sendKeyEvent = client.sendKeyEvent.bind(client);
   return iframe;
 }