Okay, bug 332176 has landed, so this is ready to implement. (It's one of the last remaining pieces needed for removing JSD...)
Panos, since you've been working on bug 961325, which is in the same neighborhood as this, would you be interested in preparing a patch for this? This one should be really simple --- just passing a const char * in at each site that passes JS source to SpiderMonkey (whether it's run immediately or not) --- and I've been promising it to the Firebug people for months, as it's one of their final blockers. The two prerequisites I mentioned above are quick patches, so hopefully they won't take long to review...
OK, I'll give it a shot.
I'll trim this down and re-post.