This is in reference to the vulnerability that Google is not patching, since the WebView in 4.3 and less is part of the OS and not a separate updateable component.
Since some people will not have easy upgrade options from their phone manufacturer or cell carrier, they might consider just staying with 4.3, or some are still hoping their carrier provides an upgrade at some point. In this case it's useful to understand what one can do to mitigate the risk of the vulnerability.
If so, is that risk mitigated by using a browser like Firefox or Chrome (that I am guessing does not use the WebView component).
Or does the vulnerability require installing an app that a developer has maliciously written to exploit the Web View component, to allow the app to perform actions that it wasn't permitted to?