Only handle click actions for left & middle buttons

chrome/browser/resources/md_downloads/crisper.js

 // Copyright (c) 2013 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.
 function assert(condition, opt_message) {
   if (!condition) {
     var message = 'Assertion failed';
     if (opt_message) message = message + ': ' + opt_message;
     var error = new Error(message);
     var global = function() {
       return this;
@@ skipping 630 matching lines @@
   return assertInstanceof($(id), HTMLElement, 'Missing required element: ' + id);
 }
 
 function queryRequiredElement(selectors, opt_context) {
   var element = (opt_context || document).querySelector(selectors);
   return assertInstanceof(element, HTMLElement, 'Missing required element: ' + selectors);
 }
 
 [ 'click', 'auxclick' ].forEach(function(eventName) {
   document.addEventListener(eventName, function(e) {
+    if (e.button !== 0 && e.button !== 1)
+      return; // Ignore buttons other than left and middle.

[Dan Beam, 2016/09/12 19:18:59]

this is a generated file

you need to update ui/webui/resources/js/util.js and re-run

chrome/browser/resources/vulcanize.py

[Navid Zolghadr, 2016/09/12 19:50:09]

Umm. That is weird. Because I changed this file in the original review and
nobody complained. Was that also incorrect?
https://codereview.chromium.org/2163893003/

I tried modifying utils.js and running vulcanize.py. I got this error running it
from chrome/browser/resources. The error exists event with the tip of the tree
without my changes. Is this error familiar?

TypeError: exceptions must be old-style classes or derived from BaseException,
not NoneType

[Dan Beam, 2016/09/12 21:25:32]

you changed both util.js and crisper.js in similar ways

that part of the exception is not useful, but i'm almost sure you need to
install dependencies

     if (e.defaultPrevented) return;
     var eventPath = e.path;
     var anchor = null;
     if (eventPath) {
       for (var i = 0; i < eventPath.length; i++) {
         var element = eventPath[i];
         if (element.tagName === 'A' && element.href) {
           anchor = element;
           break;
         }
@@ skipping 6295 matching lines @@
     Manager.get().updateItem_(index, data);
   };
   return {
     Manager: Manager
   };
 });
 
 // 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.
-window.addEventListener('load', downloads.Manager.onLoad);
+window.addEventListener('load', downloads.Manager.onLoad);