Fix 'crushed block' bug in Firefox.
Fix 'crushed block' bug in Firefox.

git-svn-id: 2cf55447cea94972d775c94cce66c944ede0459c@533 c400ca83-b69d-9dd7-9705-49c6b8615e23

tobyk100/blockly-trunk,tobyk100/blockly-trunk,tobyk100/blockly-trunk,tobyk100/blockly-trunk,tjpalmer/blockly,tjpalmer/blockly,Khan/blockly,jadonk/blockly-bonescript,jadonk/blockly-bonescript,Khan/blockly