Links in PDF should be opened in new background tabs when ctrl + left clicked.

chrome/browser/resources/pdf/navigator.js

 // Copyright 2015 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 Navigator for navigating to links inside or outside the PDF.
  * @param {string} originalUrl The original page URL.
  * @param {Object} viewport The viewport info of the page.
  * @param {Object} paramsParser The object for URL parsing.
  * @param {Function} navigateInCurrentTabCallback The Callback function that
  *    gets called when navigation happens in the current tab.
- * @param {Function} navigateInNewTabCallback The Callback function that gets
- *    called when navigation happens in the new tab.
+ * @param {Function} navigateInNewBackgroundTabCallback The Callback function
+ *    that gets called when navigation happens in the new background tab.
  */
 function Navigator(originalUrl,
                    viewport,
                    paramsParser,
                    navigateInCurrentTabCallback,
-                   navigateInNewTabCallback) {
+                   navigateInNewBackgroundTabCallback) {
   this.originalUrl_ = originalUrl;
   this.viewport_ = viewport;
   this.paramsParser_ = paramsParser;
   this.navigateInCurrentTabCallback_ = navigateInCurrentTabCallback;
-  this.navigateInNewTabCallback_ = navigateInNewTabCallback;
+  this.navigateInNewBackgroundTabCallback_ = navigateInNewBackgroundTabCallback;
 }
 
 Navigator.prototype = {
   /**
    * @private
    * Function to navigate to the given URL. This might involve navigating
    * within the PDF page or opening a new url (in the same tab or a new tab).
    * @param {string} url The URL to navigate to.
    * @param {boolean} newTab Whether to perform the navigation in a new tab or
    *    in the current tab.
@@ skipping 15 matching lines @@
     }
 
     // If there's no scheme, then take a guess at the scheme.
     if (url.indexOf('://') == -1 && url.indexOf('mailto:') == -1)
       url = this.guessUrlWithoutScheme_(url);
 
     if (!this.isValidUrl_(url))
       return;
 
     if (newTab) {
-      this.navigateInNewTabCallback_(url);
+      this.navigateInNewBackgroundTabCallback_(url);
     } else {
       this.paramsParser_.getViewportFromUrlParams(
           url, this.onViewportReceived_.bind(this));
     }
   },
 
   /**
    * @private
    * Called when the viewport position is received.
    * @param {Object} viewportPosition Dictionary containing the viewport
@@ skipping 95 matching lines @@
     if (isRelative) {
       var slashIndex = this.originalUrl_.lastIndexOf('/');
       var path = slashIndex != -1 ?
           this.originalUrl_.substr(0, slashIndex) : this.originalUrl_;
       return path + '/' + url;
     }
 
     return 'http://' + url;
   }
 };