Pressing on that icon should allow you to run java once, or allow if forever for that site.
If the icon doesn't appear, I think you should file a bug on bugzilla.
I've yet to see a single non-technical user even notice or react to its presence once. I see it instantly and can't understand why it doesn't alert or annoy them, but to them, it's just not there.
In light of that sort of behaviour, adding a subtle icon to the location bar is meaningless. Heck, adding anything to the location bar is meaningless if the intent is to communicate with the user; most users never look there.
So yeah. If that's Mozilla's stance, they will find out that nobody's going to notice. I certainly didn't see it. That is effectively dead code which they've written.