src/vs/base/browser/dom.ts/getContentHeight
export function getContentHeight(element: HTMLElement): number {
	let border = SizeUtils.getBorderTopWidth(element) + SizeUtils.getBorderBottomWidth(element);
	let padding = SizeUtils.getPaddingTop(element) + SizeUtils.getPaddingBottom(element);
	return element.offsetHeight - border - padding;
}