Bug 849996. Check the correct frame for transforms in PushAbsoluteContainingBlock --- it might not be the containing block itself. r=bzbarsky
Bug 862180. Part 1: Remove null checks on the result of nsDisplayItem::GetUnderlyingFrame(). r=mattwoodrow
Bug 862180. Part 2: Rename nsDisplayItem::GetUnderlyingFrame() to Frame(). r=mattwoodrow