src/vs/editor/common/model/prefixSumComputer.ts/ConstantTimePrefixSumComputer/setValue
class ConstantTimePrefixSumComputer:	public setValue(index: number, value: number): void {
		if (this._values[index] === value) {
			// no change
			return;
		}
		this._values[index] = value;
		this._invalidate(index);
	}