There are a bunch of force conversion between float and LayoutUnit in sticky offset computation, this can result in incorrect snapping.

The right way is to store the local rects in LayoutRect in StickyPositionScrollingConstraints, and compute the PixelSnappedIntRect during paint time with paint offset (or subpixel accumulation) applied. The cc::LayerStickyPositionConstraint theoretically only need integer rects.