When digesting JavaScript performance issues it's much easier to drill down the flamegraph in JS-only mode. For that the GC times are often very relevant to see. One can always switch back and forth between the All stacks and the JavaScript view, but that's tedious and filled with with a lot of noise which is not as relevant for a web developer as it may be for those working on firefox itself.
Full view "All stacks":

JavaScript view:

So the idea is if we can show a combined bar for GC times in the JavaScript view. Just a single bar that displays the total GC time at that point:

┆Issue is synchronized with this Jira Task
When digesting JavaScript performance issues it's much easier to drill down the flamegraph in JS-only mode. For that the GC times are often very relevant to see. One can always switch back and forth between the
All stacksand theJavaScriptview, but that's tedious and filled with with a lot of noise which is not as relevant for a web developer as it may be for those working on firefox itself.Full view "All stacks":
JavaScript view:
So the idea is if we can show a combined bar for GC times in the JavaScript view. Just a single bar that displays the total GC time at that point:
┆Issue is synchronized with this Jira Task