src/vs/editor/common/viewLayout/linesLayout.ts/LinesLayout/getWhitespacesTotalHeight
class LinesLayout:	public getWhitespacesTotalHeight(): number {
		this._checkPendingChanges();
		if (this._arr.length === 0) {
			return 0;
		}
		return this.getWhitespacesAccumulatedHeight(this._arr.length - 1);
	}