closure = function() {
      Blockly.BlockSvg.disposeUiStep_(clone, rtl, start, workspaceScale);
    }
Animate a cloned block and eventually dispose of it.
This is a class method, not an instace method since the original block has
been destroyed and is no longer accessible.
@param {!Element} clone SVG element to animate and dispose of.
@param {boolean} rtl True if RTL, false if LTR.
@param {!Date} start Date of animation's start.
@param {number} workspaceScale Scale of workspace.
@private