function findPreviousToken(textRange)
        {
            var line = textEditor.line(textRange.startLine);
            if (textRange.startColumn < 3 || line[textRange.startColumn - 1] !== ".")
                return null;
            var token = textEditor.tokenAtTextPosition(textRange.startLine, textRange.startColumn - 2);
            return token ? line.substring(token.startColumn, token.endColumn) : null;
        }
@param {!WebInspector.TextRange} textRange
@return {?string}