Just updated a client's project from 3.3 to 3.4 and now getting JS errors in console in both Firefox and Chrome, caused by https://github.com/symfony/symfony/blob/master/src/Symfony/Bundle/WebProfilerBundle/Resources/views/Profiler/base_js.html.twig#L125

The error is:

TypeError: tbody.rows.count is not a function

After setting a breakpoint in the Chrome debugger, it looks like tbody.rows is an HTMLCollection. According to https://developer.mozilla.org/en-US/docs/Web/API/HTMLCollection, it has no count method. That line should probably be tbody.rows.length