Fixes button :active state on firefox #12126

When doing event.preventDefault() firefox will not trigger the :active
selector intentionally (see
https://bugzilla.mozilla.org/show_bug.cgi?id=771241).

Event.preventDefault() was added to prevent text selection in #10917
but it actually is not needed since the button also uses the
user-select:none css attribute which effectivly prevents the text selection.

Also now applying the previously browser specific (ie,opera) .v-pressed
classname to all browsers to make styling of the pressed state a bit easier
to do for all browsers and not reliant on the :active pseudo-class which is a
non-standard pseudo-class.

Change-Id: Ic67c0abb9d0bf8f47b817609f2928aa8fff3e82b