src/vs/editor/common/viewModel.ts/OverviewRulerDecorationsGroup/cmp
class OverviewRulerDecorationsGroup:	public static cmp(a: OverviewRulerDecorationsGroup, b: OverviewRulerDecorationsGroup): number {
		if (a.zIndex === b.zIndex) {
			if (a.color < b.color) {
				return -1;
			}
			if (a.color > b.color) {
				return 1;
			}
			return 0;
		}
		return a.zIndex - b.zIndex;
	}