src/vs/editor/common/viewLayout/linesLayout.ts/LinesLayout/getWhitespaceAccumulatedHeightBeforeLineNumber
class LinesLayout:	public getWhitespaceAccumulatedHeightBeforeLineNumber(lineNumber: number): number {
		this._checkPendingChanges();
		lineNumber = lineNumber | 0;

		const lastWhitespaceBeforeLineNumber = this._findLastWhitespaceBeforeLineNumber(lineNumber);

		if (lastWhitespaceBeforeLineNumber === -1) {
			return 0;
		}

		return this.getWhitespacesAccumulatedHeight(lastWhitespaceBeforeLineNumber);
	}