Created attachment 272744 [details] testcase CheckFontCallback needs to consider the 'larger' and 'smaller' values of 'font-size', which mean that the value on the element is derived from its parent. (We set aInherited correctly in nsRuleNode::SetFont, but we need to get it right here as well so we know to get the real parentFont rather than the bogus one.) Bug 383979 will make this show up in more cases.
Created attachment 272747 [details] testcase that only shows up with bug 383979 landed This is probably a more likely testcase to show up in the real world. Thus this blocks bug 383979.
Created attachment 272748 [details] [diff] [review] patch
Comment on attachment 272748 [details] [diff] [review] patch r+sr=bzbarsky. I really wish we didn't duplicate logic like this between the check callbacks and the actual computation. :(
Fix checked in to trunk.