Issue 6557: Font previews don't work

Conflicts:
	extension/content/firebug/css/cssReps.js
	extension/content/firebug/js/debugger.js
	extension/content/firebug/net/tabCache.js
Modifications added from original commit:
	extension/content/firebug/debugger/script/sourceFileRenamer.js
Issue 6778: Cross-domain log messages aren't displayed within the console