src/vs/editor/browser/view/viewLayer.ts/RenderedLinesCollection/getLine
class RenderedLinesCollection:	public getLine(lineNumber: number): T {
		const lineIndex = lineNumber - this._rendLineNumberStart;
		if (lineIndex < 0 || lineIndex >= this._lines.length) {
			throw new Error('Illegal value for lineNumber');
		}
		return this._lines[lineIndex];
	}