[web] write css_class to attrs on rendering and not on button creation
Because css_class attribute may be overriden by bootstrap after button creation and this
modification has to be taken into account.
closes #5457548
/*
* cubicweb js mock for unit tests
* This module defines variables and functions used in quite a few places
* in cw js framework that can't be used or guessed without a real CW server
*/
var pageid = 'my-page-id';
function _(message) {
return message;
}