src/vs/editor/common/viewLayout/viewLayout.ts/ViewLayout/saveState
class ViewLayout:	public saveState(): { scrollTop: number; scrollTopWithoutViewZones: number; scrollLeft: number } {
		const currentScrollPosition = this._scrollable.getFutureScrollPosition();
		const scrollTop = currentScrollPosition.scrollTop;
		const firstLineNumberInViewport = this._linesLayout.getLineNumberAtOrAfterVerticalOffset(scrollTop);
		const whitespaceAboveFirstLine = this._linesLayout.getWhitespaceAccumulatedHeightBeforeLineNumber(firstLineNumberInViewport);
		return {
			scrollTop: scrollTop,
			scrollTopWithoutViewZones: scrollTop - whitespaceAboveFirstLine,
			scrollLeft: currentScrollPosition.scrollLeft
		};
	}