Sub-pixel coordinate granularity

Hi,
The latest CSSOM view editors draft extends a number of APIs (including
MouseEvent) to use 'double' for co-ordinates instead of 'int' (
http://dev.w3.org/csswg/cssom-view/#extensions-to-the-mouseevent-interface).
 Since PointerEvent extends MouseEvent, we'd get this improved definition
"for free".  I think this is valuable, for example, when implementing
javscript-driven touch dragging or scrolling which should be just as smooth
as native browser scrolling.

Thoughts?
   Rick