Repro: https://output.jsbin.com/luzuyab

Scroll down quickly with mouse wheel on Linux / Windows / CrOS.  There should not be any red.

This is also the root cause of something I've noticed for a while which is that scrolling up has a tendency to settle at scrollTop == 1px when it should have had enough inertia to hit the top.  When the target is at a scroll bound, new wheel events produce a slight overscroll in the cc::LayerImpl which is clamped to 0 by FrameView during applyViewportDeltas.  Then when the curve returns to 0 we apply a positive delta to the already-clamped scroll offset.

Patch in progress.