 value')) {             return null;         }         var start = this.index;         var startingColumn = this.column;         var startingLine = this.line;         this.advance();         this.advance();         while (!isCommentEnd(this.peek, this.peekPeek)) {             if (this.peek == chars.$EOF) {                 this.error('Unterminated comment');             }             this.advance();         }         this.advance();         this.advance();         var str = this.input.substring(start, this.index);         return new CssToken(start, startingColumn, startingLine, CssTokenType.