from the context menu (or anywhere really) causes the workspace to
recalculate its size.
Remove the call to svgResizeContents from onMouseUp's logic for
determining whether the block is being dropped in the trash
since it calls dispose.
One side effect of this is that when you delete multiple blocks
resize gets called for each of them and the scrollbars move during
the operation. This is most obviously seen by doing an airstrike
in the playground and then deleting all the blocks at once.
567fe6a2e8