I was testing my changes to about:support and saw an assertion failure when trying to load about:support. It turned out the assertion failure happens even before my changes. This build, for example, triggers it: http://ftp.mozilla.org/pub/mozilla.org/firefox/tinderbox-builds/mozilla-central-win32-debug/1281731664/ The assertion is as follows. ###!!! ASSERTION: bad hint in chrome code: 'hint != XOW && hint != SOW && hint != COW', file e:/builds/moz2_slave/mozilla-central-win32-debug/build/js/src/xpconnect/src/xpcwrappednativescope.cpp, line 1055
The code that causes this assertion went away with compartments.