Triple-Click Detection for IE

IE does not properly support MouseEvent.detail for reporting the number of clicks in a user action. The new clickCounter() function takes a mousedown event and returns the detail property if non-IE or calculates the detail by comparing to a recent history (up to 3) of mousedowns.

Change-Id: Ib521eaa695d7e436d67ebb49106159daadc2ee38
Merge "Triple-Click Detection for IE"