Fix for PDFs with lots of named destinations take a long time to load.

chrome/browser/resources/pdf/open_pdf_params_parser.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';
 
 /**
  * Creates a new OpenPDFParamsParser. This parses the open pdf parameters
  * passed in the url to set initial viewport settings for opening the pdf.
+ * @param {Object} getNamedDestinationsFunction The function called to fetch
+ *     the page number for a named destination.
  */
-function OpenPDFParamsParser() {
-  // A dictionary of all the named destinations in the PDF.
-  this.namedDestinations = {};
+function OpenPDFParamsParser(getNamedDestinationsFunction) {
+  this.outstandingRequests_ = [];
+  this.getNamedDestinationsFunction_ = getNamedDestinationsFunction;
 }
 
 OpenPDFParamsParser.prototype = {
   /**
    * @private
    * Parse zoom parameter of open PDF parameters. If this
    * parameter is passed while opening PDF then PDF should be opened
    * at the specified zoom level.
    * @param {number} zoom value.
    * @param {Object} viewportPosition to store zoom and position value.
@@ skipping 21 matching lines @@
     viewportPosition['zoom'] = zoomFactor;
   },
 
   /**
    * @private
    * Parse PDF url parameters. These parameters are mentioned in the url
    * and specify actions to be performed when opening pdf files.
    * See http://www.adobe.com/content/dam/Adobe/en/devnet/acrobat/
    * pdfs/pdf_open_parameters.pdf for details.
    * @param {string} url that needs to be parsed.
-   * @return {Object} A dictionary containing the viewport which should be
-   * displayed based on the URL.
+   * @param {Function} callback function to be called with viewport info.
    */
-  getViewportFromUrlParams: function(url) {
+  getViewportFromUrlParams: function(url, callback) {
     var viewportPosition = {};
+    viewportPosition['url'] = url;
     var paramIndex = url.search('#');
-    if (paramIndex == -1)
-      return viewportPosition;
+    if (paramIndex == -1) {
+      callback(viewportPosition);
+      return;
+    }
 
     var paramTokens = url.substring(paramIndex + 1).split('&');
     if ((paramTokens.length == 1) && (paramTokens[0].search('=') == -1)) {
       // Handle the case of http://foo.com/bar#NAMEDDEST. This is not
-      // explicitlymentioned except by example in the Adobe
+      // explicitly mentioned except by example in the Adobe
       // "PDF Open Parameters" document.
-      viewportPosition['page'] = this.namedDestinations[paramTokens[0]];
-      return viewportPosition;
+      this.outstandingRequests_.push({
+        callback: callback,
+        viewportPosition: viewportPosition
+      });
+      this.getNamedDestinationsFunction_(paramTokens[0]);
+      return;
     }
 
     var paramsDictionary = {};
     for (var i = 0; i < paramTokens.length; ++i) {
       var keyValueSplit = paramTokens[i].split('=');
       if (keyValueSplit.length != 2)
         continue;
       paramsDictionary[keyValueSplit[0]] = keyValueSplit[1];
     }
 
-    if ('nameddest' in paramsDictionary) {
-      var page = this.namedDestinations[paramsDictionary['nameddest']];
-      if (page != undefined)
-        viewportPosition['page'] = page;
-    }
-
     if ('page' in paramsDictionary) {
       // |pageNumber| is 1-based, but goToPage() take a zero-based page number.
       var pageNumber = parseInt(paramsDictionary['page']);
       if (!isNaN(pageNumber) && pageNumber > 0)
         viewportPosition['page'] = pageNumber - 1;
     }
 
     if ('zoom' in paramsDictionary)
       this.parseZoomParam_(paramsDictionary['zoom'], viewportPosition);
 
-    return viewportPosition;
-  }
+    if (viewportPosition.page === undefined &&
+        'nameddest' in paramsDictionary) {
+      this.outstandingRequests_.push({
+        callback: callback,
+        viewportPosition: viewportPosition
+      });
+      this.getNamedDestinationsFunction_(paramsDictionary['nameddest']);
+    } else {
+      callback(viewportPosition);
+    }
+  },
+
+  /**
+   * This is called when a named destination is received and the page number
+   * corresponding to the request for which a named destination is passed.
+   * @param {number} pageNumber The page corresponding to the named destination
+   *    requested.
+   */
+  onNamedDestinationReceived: function(pageNumber) {
+    var outstandingRequest = this.outstandingRequests_.shift();
+    if (pageNumber != -1)
+      outstandingRequest.viewportPosition.page = pageNumber;
+    outstandingRequest.callback(outstandingRequest.viewportPosition);
+  },
 };