Bug 961871 - Part 1: Refactor ScrollingActive. r=mattwoodrow
Bug 961871 - Part 2: Refactor will-change scroll, pass through a nsDisplayListBuilder. r=mattwoodrow
Bug 961871 - Part 3: Implement will-change budgeting. r=roc
Bug 961871 - Part 4: Fix budget calculation by adding Maybe prerenderer and animate. r=roc