mbostock/d3 — pull request #1934 by mbostock (2014-07-07 04:38:08+00:00)
Title: Fix #1933 - set zoom center on zoomstart.

Rather than set the zoom center on the first mousewheel following a mousemove, we now set the zoom center on the first mousewheel event of a zoom gesture. This is slightly simpler logic and avoids confusing behavior during constrained momentum scrolling.