openlayers/ol3 — pull request #2975 by fredj (2014-11-27 08:30:56+00:00)
Title: Use offsetX and offsetY if available

Use the mouse event `offsetX` and `offsetY` properties if available instead of computing the value in javascript.
See http://www.w3.org/TR/cssom-view/#dom-mouseevent-pagex

work in progress: needs more tests on IE