Created attachment 268224 [details] Reduced testcase (Don't ask me why anyone would use font-variant: small-caps with Tamil) On loading http://ta.wikipedia.org I get lots of the following: ###!!! ASSERTION: lost some break-before values?: 'canBreakBeforeArray.Length() == i - runStart', file c:/mozdev/worktree/mozilla/layout/generic/nsTextRunTransformations.cpp, line 405 ###!!! ASSERTION: Break suggested inside cluster!: '!aBreakBefore[i] || mCharacterGlyphs[aStart + i].IsClusterStart()', file c:/mozdev/worktree/mozilla/gfx/thebes/src/gfxFont.cpp, line 700 On Windows at least, the text is rendered correctly to the best of my knowledge.
I checked in a fix for this.