_getLineNumberFor(domNode) {
        const startLineNumber = this._visibleLines.getStartLineNumber();
        const endLineNumber = this._visibleLines.getEndLineNumber();
        for (let lineNumber = startLineNumber; lineNumber <= endLineNumber; lineNumber++) {
            const line = this._visibleLines.getVisibleLine(lineNumber);
            if (domNode === line.getDomNode()) {
                return lineNumber;
            }
        }
        return -1;
    }
@returns the line number of this view line dom node.