delta_multiplier_(x|y|z) prefs don't support < 100 values and > -100 values. I guess that we need to take additional care fractional delta values of DOM_DELTA_PIXEL.
Created attachment 652326 [details] [diff] [review] Patch The fix for bug 422132 makes this patch simple. The DeltaAccumulator::mPendingScrollAmount(X|Y) supports scrolling less than 1px. So, this patch just removes the pref value checking and avoiding zero divide. I think that if all delta values become 0 by the prefs, the wheel event shouldn't cause DOM event.