mbostock/d3 — pull request #1498 by jasondavies (2013-08-30 22:14:42+00:00)
Title: Support simultaneous zooming on multiple targets.

Fixes #1497, where a zoom gesture would break if a touch was started
outside the target during a gesture.

Each zoom gesture now only considers touches that were started on its
associated target element. This allows multiple zoom gestures to occur
at once without conflicts.