Discussion: have a common visual gimmick to indicate something is "on"

In several issues we've seen the need to have a visual cue that something is on:

* filter by search string #164
* inverted call stack #94
* hidden tracks (the current implementation makes it very (too much) visible IMO)

My current idea is to have a quite thick blue border on one edge (could be done with either box-shadow or outline), not unlike how the active tab is done in Firefox.

This is especially a problem when a user follows a link to a profile with some filtering already enabled.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-132)