src/vs/editor/common/viewModel/viewModelImpl.ts/HiddenAreasModel/getMergedRanges
class HiddenAreasModel:	getMergedRanges(): readonly Range[] {
		if (!this.shouldRecompute) {
			return this.ranges;
		}
		this.shouldRecompute = false;
		const newRanges = Array.from(this.hiddenAreas.values()).reduce((r, hiddenAreas) => mergeLineRangeArray(r, hiddenAreas), []);
		if (rangeArraysEqual(this.ranges, newRanges)) {
			return this.ranges;
		}
		this.ranges = newRanges;
		return this.ranges;
	}