b=810274 include bounds with layer pixels as possible destinations to minimize subpixel scrolls r=roc

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extra : transplant_source : a%E1S%03%CBB%D3%DE%DDn%96r%BC%B2%D6%7D%82%AB%EBv
b=810274 allow smooth scroll step to nearest pixel boundary short of desired position r=roc

--HG--
extra : transplant_source : %BE%DF%8BhHLmaB%D5%3F%DD7%AB%14%989%A0%CA%14
backout bug 810274 for typeof VS compile failure
Bug 864120 - Use a display list item to create the focus ring for <input type=range>. r=roc