src/vs/workbench/browser/layout.ts/Layout/setActivityBarHidden
class Layout:	private setActivityBarHidden(hidden: boolean, skipLayout?: boolean): void {
		// Propagate to grid
		this.stateModel.setRuntimeValue(LayoutStateKeys.ACTIVITYBAR_HIDDEN, hidden);
		this.workbenchGrid.setViewVisible(this.activityBarPartView, !hidden);
	}