* Fix#1275 by adding a more specific rule for overflow:visible on the drag surface svg. This wins out over a common bootstrap rule that says: svg:not(:root) {overflow:hidden} and helps avoid a difficult problem for Blockly users to diagnose.
* Update css.js
* Change the setting of the CSS transform properties on SVG nodes to set both the unprefixed version and the `-webkit-` prefixed version so that Blockly correctly renders in order browsers, such as Safari < 9 and iOS Safari < 9.2. For discussion of this issue, see https://groups.google.com/forum/#!topic/blockly/o3pERaRQhSg
* Correct the separation between the CSS transform property and the rest of the CSS that was in the variable misleadingly called "transform".
* Add a workspace drag surface that blocks and bubble get moved to during a workspace drag.
The surface is translated using translate3d instead of svg's translate attribute so that
the browser does not have to repaint the entire workspace on every mouse move.
This is very similar to the block drag surface.
* Address code review comments
* add back hasClass_ utility removed in #748 and stop using contains since it is not supported in IE
