src/vs/editor/browser/viewParts/scrollDecoration/scrollDecoration.ts/ScrollDecorationViewPart/_updateShouldShow
class ScrollDecorationViewPart:	private _updateShouldShow(): boolean {
		const newShouldShow = (this._useShadows && this._scrollTop > 0);
		if (this._shouldShow !== newShouldShow) {
			this._shouldShow = newShouldShow;
			return true;
		}
		return false;
	}