Modify pdf_scripting_api.js to support postMessage using BrowserPlugin

chrome/browser/resources/pdf/main.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.
 
 'use strict';
 
 /**
  * Global PDFViewer object, accessible for testing.
  * @type Object
  */
 var viewer;
 
-/**
- * Entrypoint for starting the PDF viewer. This function obtains the details
- * of the PDF 'stream' (the data that points to the PDF) and constructs a
- * PDFViewer object with it.
- */
-(function main() {
-  // If the viewer is started from the browser plugin, the view ID will be
-  // passed in which identifies the instance of the plugin.
-  var params = window.location.search.substring(1).split('=');
-  if (params.length == 2 && params[0] == 'id') {
-    var viewId = params[1];
 
-    // Send a message to the background page to obtain the stream details. It
-    // will run the callback function passed in to initialize the viewer.
-    chrome.runtime.sendMessage(
-        'mhjfbmdgcfjbbpaeojofohoefgiehjai',
-        {viewId: viewId},
-        function(streamDetails) { viewer = new PDFViewer(streamDetails); });
-    return;
+(function() {
+  /**
+   * Stores any pending messages received which should be passed to the
+   * PDFViewer when it is created.
+   * @type Array
+   */
+  var pendingMessages = [];
+
+  /**
+   * Handles events that are received prior to the PDFViewer being created.
+   * @param {Object} message A message event received.
+   */
+  function handleScriptingMessage(message) {
+    pendingMessages.push(message);
   }
 
-  // The viewer may be started directly by passing in the URL of the PDF to load
-  // as the query string. This is used for print preview in particular. The URL
-  // of this page will be of the form
-  // 'chrome-extension://<extension id>?<pdf url>'. We pull out the <pdf url>
-  // part here.
-  var url = window.location.search.substring(1);
-  var streamDetails = {
-    streamUrl: url,
-    originalUrl: url,
-    responseHeaders: '',
-    embedded: window.parent != window,
-    tabId: -1
-  };
-  if (!chrome.tabs) {
+  /**
+   * Initialize the global PDFViewer and pass any outstanding messages to it.
+   * @param {Object} streamDetails The stream object which points to the data
+   *     contained in the PDF.
+   */
+  function initViewer(streamDetails) {
+    // PDFViewer will handle any messages after it is created.
+    window.removeEventListener('message', handleScriptingMessage, false);
     viewer = new PDFViewer(streamDetails);
-    return;
+    while (pendingMessages.length > 0)
+      viewer.handleScriptingMessage(pendingMessages.shift());
   }
-  chrome.tabs.getCurrent(function(tab) {
-    if (tab && tab.id != undefined)
-      streamDetails.tabId = tab.id;
-    viewer = new PDFViewer(streamDetails);
-  });
+
+  /**
+   * Entrypoint for starting the PDF viewer. This function obtains the details
+   * of the PDF 'stream' (the data that points to the PDF) and constructs a
+   * PDFViewer object with it.
+   */
+  function main() {
+    // Set up an event listener to catch scripting messages which are sent prior
+    // to the PDFViewer being created.
+    window.addEventListener('message', handleScriptingMessage, false);
+
+    // If the viewer is started from the browser plugin, the view ID will be
+    // passed in which identifies the instance of the plugin.
+    var params = window.location.search.substring(1).split('=');
+    if (params.length == 2 && params[0] == 'id') {
+      var viewId = params[1];
+
+      // Send a message to the background page to obtain the stream details. It
+      // will run the callback function passed in to initialize the viewer.
+      chrome.runtime.sendMessage(
+          'mhjfbmdgcfjbbpaeojofohoefgiehjai',
+          {viewId: viewId},
+          initViewer);
+      return;
+    }
+
+    // The viewer may be started directly by passing in the URL of the PDF to
+    // load as the query string. This is used for print preview in particular.
+    // The URL of this page will be of the form
+    // 'chrome-extension://<extension id>?<pdf url>'. We pull out the <pdf url>
+    // part here.
+    var url = window.location.search.substring(1);
+    var streamDetails = {
+      streamUrl: url,
+      originalUrl: url,
+      responseHeaders: '',
+      embedded: window.parent != window,
+      tabId: -1
+    };
+    if (!chrome.tabs) {
+      initViewer(streamDetails);
+      return;
+    }
+    chrome.tabs.getCurrent(function(tab) {
+      if (tab && tab.id != undefined)
+        streamDetails.tabId = tab.id;
+      initViewer(streamDetails);
+    });
+  }
+
+  main();
 })();