src/vs/editor/browser/view/viewLayer.ts/ViewLayerRenderer/_insertLinesBefore
class ViewLayerRenderer:	private _insertLinesBefore(ctx: IRendererContext<T>, fromLineNumber: number, toLineNumber: number, deltaTop: number[], deltaLN: number): void {
		const newLines: T[] = [];
		let newLinesLen = 0;
		for (let lineNumber = fromLineNumber; lineNumber <= toLineNumber; lineNumber++) {
			newLines[newLinesLen++] = this.host.createVisibleLine();
		}
		ctx.lines = newLines.concat(ctx.lines);
	}