I thinks this coincides with a play services update. YouTube especially can be made to crash quite reliably (just watch a video, you won't get to more than a few minutes).
I'm unsure if Firefox is related, probably is. It's somewhat crash happy anyway, but it's got worse the last couple of days. YouTube is more reliable to crash so I'll stick with that and hope for the best.
Managed to grab this from logcat:
Before that, there was literally thousands of "Mapbox" lines showing as well. These lines repeat again and again:
05-26 09:40:47.496 26675 26675 E Mapbox : [telemetry]: Unable to start location collection: Unknown(startMonitorAppOp returned MODE_IGNORED)
05-26 09:40:47.498 26675 26675 E Mapbox : [LiveTrackingClient]: Failed to start: java.lang.SecurityException: startMonitorAppOp returned MODE_IGNORED