Comment 64 for bug 572074

Created attachment 8642998
middlemouse on new tab button creates a new tab related to current

Workarounds involve duplicating the current tab or opening a link in a new related tab but these don't show the new tab page and are less responsive.

Ideally there should be a context menu entry like other browsers (Chrome, IE11) but considering that adding a "Duplicate Tab" entry was opposed (Bug 455722) it looks like we have to resort to other methods. The middlemouse approach (Bug 448546) seems like a valid alternative and is currently unutilized for the new tab button.

Here's a patch to make middlemouse/ctrl-click on the new tab button create a new tab related to the current tab.

It uses whereToOpenLink() so it is consistent with other middlemouse usage.
It uses standard related tab behavior, adding the new tab after other related tabs.
It needs to exclude commands that originate from keypresses so that Ctrl+T behaves normally.