title: SVG clipping in D3 brush doesn't work in Firefox
body: <p>Using M. Bostock's example of <a href="https://bl.ocks.org/mbostock/1667367" rel="nofollow">focus + context</a>, I'm trying to implement date selection via brushing: <a href="http://clflwd.org/lake-test.php" rel="nofollow">http://clflwd.org/lake-test.php</a>.  It's working fine in Chrome and IE, but in Firefox the path overflows the chart during brushing.</p>