Dispatch middle click manually by tracking mouse

chrome/browser/resources/ntp4/middleclick_gen.js

+// Copyright (c) 2016 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.
+var middleButtonMouseDownTarget = null;
+document.addEventListener('mousedown', function(e) {
+  if (e.button == 1) {
+    middleButtonMouseDownTarget = e.target;
+  }
+}, true);
+document.addEventListener('mouseup', function(e) {
+  if (e.button == 1 && e.target == middleButtonMouseDownTarget) {
+    e.target.dispatchEvent(new MouseEvent('click', e));

[dtapuska, 2016/05/10 12:27:15]

The middleButtonMouseDownTarget should always likely get cleared when it is up
in order to avoid a memory leak.

[Navid Zolghadr, 2016/05/10 13:17:40]

I don't quite understand what you are suggesting here. Do you mean I should set
that to null without any check? Say for example even when mouseup with button=0
happens?
If I do that I break an edge scenario here as well which might not be important.
If you left press outside of the icon and middle press and left release and
middle release inside in the older version of Chrome that would open the app in
the new page. If I clear that variable for any mouseup it doesn't. Although that
is an edge scenario and I don't think it is at all important. Having said that,
do you want me to still clear this variable all the time on mouseup?
Note that the memory leak you are talking about is inevitable as mouse can go
outside of the page without us getting any event at all (not even the leave
event) when for example user does Alt+Tab.

+    middleButtonMouseDownTarget = null;
+  }
+}, true);