bug 837461 - backout parts 2 and 3 of bug 808288 because pdf.js may paint missing chars to canvas if it failed to load fonts, which looks really ugly; better to skip them for now. r=bas a=akeybl
bug 817454 - ensure PresContext's cached mAppUnitsPerDevPixel value is updated when backing resolution changes. r=roc a=bajaj
bug 829963 - fix hi-/lo-dpi scaling in window opened from script with explicit size on secondary display. r=roc a=bajaj