Created attachment 620265 [details]
###!!! ASSERTION: Whoever was caching this font group should have called UpdateFontList on it: '!mUserFontSet || mCurrGeneration == GetGeneration()', file ../../../gfx/thebes/gfxFont.h, line 3002
(Similar to bug 745699, which was fixed two weeks ago.)
Created attachment 620280 [details] [diff] [review]
patch, ensure the font list is updated
Ah yes - the use of ctx.measureText("") bypasses the fix that was landed for bug 745699, as the zero-length string doesn't cause us to actually create a text run. So we need to explicitly make sure the font list is updated before accessing its first font's metrics here.