When VE is initialized, there is a call to ve.ui.Toolbar#calculateOffset, to calculate the left and right offsets of the toolbar. But the offsets should be the same as div#content, so we could compute the offsets earlier, when we're still waiting for the API response. Ed thinks that this is sensible, but he points out that there is a possible edge case to account for, when switching to VE changes whether or not you have a scroll bar.