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} getNamedDestination to fectch page number for
+ * namedDestination.
  */
-function OpenPDFParamsParser() {
-  // A dictionary of all the named destinations in the PDF.
+function OpenPDFParamsParser(getNamedDestination) {
+  // A dictionary of all the named destinations in the PDF for testing.
   this.namedDestinations = {};
+  this.outstandingRequests_ = [];
+  this.getNamedDestination_ = getNamedDestination;

[raymes, 2015/02/16 02:02:30]

nit: getNamedDestinationFunction_

[Deepak, 2015/02/16 06:45:38]

Done.

 }
 
 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 {Object} callback function to be called with viewport info.

[raymes, 2015/02/16 02:02:30]

nit: {Function}

[Deepak, 2015/02/16 06:45:38]

Done.

    */
-  getViewportFromUrlParams: function(url) {
+  getViewportFromUrlParams: function(url, callback) {
     var viewportPosition = {};
     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
       // "PDF Open Parameters" document.
       viewportPosition['page'] = this.namedDestinations[paramTokens[0]];

[raymes, 2015/02/16 02:02:30]

Let's not bother caching the namedDestinations here, I don't think it will be
particularly useful. So we can remove this line and the 4 below and always just
go to the plugin.

[Deepak, 2015/02/16 06:45:38]

This is done for testcases. As we don't want to load real page.
And we are putting values in namedDestinations in the test case.
so we are not fetching page number for named destination from plugin for test
cases.

[raymes, 2015/02/16 22:44:03]

I still don't think I agree - I think we should change it. For test cases we can
use a fake getNamedDestinations function and call onNamedDestinationReceived
directly.

-      return viewportPosition;
+      if (viewportPosition['page'] != undefined) {
+        callback(viewportPosition);
+        return;
+      }
+
+      this.outstandingRequests_.push({
+        callback: callback,
+        viewportPosition: viewportPosition
+      });
+      this.getNamedDestination_(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 ('nameddest' in paramsDictionary) {
+      viewportPosition['page'] =
+          this.namedDestinations[paramsDictionary['nameddest']];
+      if (viewportPosition['page'] != undefined) {
+        callback(viewportPosition);
+        return;
+      }

[raymes, 2015/02/16 02:02:30]

Same here - let's remove the above few lines and remove this.namedDestinations
altogether

[Deepak, 2015/02/16 06:45:38]

Same reason as above.

+      this.outstandingRequests_.push({
+        callback: callback,
+        viewportPosition: viewportPosition
+      });
+      this.getNamedDestination_(paramsDictionary['nameddest']);
+      return;
+    }
+    callback(viewportPosition);
+    return;
+  },
+
+  /**
+   * It fetch outstanding request if any then update page number for
+   * namedDestination and call callback with viewport info.

[raymes, 2015/02/16 02:02:31]

This is called when a named destination is received and the page number
corresponding to the request for a named destination is passed in. 

[Deepak, 2015/02/16 06:45:38]

Done.

+   * @param {number} pageNumber for viewport.

[raymes, 2015/02/16 02:02:31]

nit: pageNumber The page corresponding to the named destination requested.

[Deepak, 2015/02/16 06:45:38]

Done.

+   */
+  onNamedDestinationReceived: function(pageNumber) {
+    var outstandingRequest = this.outstandingRequests_.shift();
+    if (!outstandingRequest)
+      return;
+    if (!outstandingRequest.viewportPosition.page)
+      outstandingRequest.viewportPosition.page = pageNumber;
+    outstandingRequest.callback(outstandingRequest.viewportPosition);
+  },
 };