[Flashblock] Flashblock and Firefox 1.5

[Philip Chee]

> Note to self:

> In Flashblock 1.5 branch remove all the code from flashblock.js that
> reference userContent.css (read/write/IO) since we are now using
> nsIStylesheetService.

Nix on that, we still need to remove the flashblock entry
from userContent.css if migrating from a profile that
was previously used on firefox 1.0.x. Currently I have
that code in a pref observer, should move the test to the
onload handler.

p.s. mozdev CVS is down again. Grrr.