anchor.diff:     * underlying source.
      *
      * This is used for string literals that contain no escapes.
  -   */
  -  String getString(int start, int end);
  +   *
  +   * The [bits] integer is an upper bound on the code point in the range
  +   * from `start` to `end`.
  +   * Usually found by doing bitwise or of all the values.
  +   * The function may choose to optimize depending on the value.
  +   */
  +  String getString(int start, int end, int bits);
   
     /**
      * Parse a slice of the current chunk as an integer.
  
positive.code: 
    int getChar(int position) => chunk.codeUnitAt(position);
  
    String getString(int start, int end) {
      return chunk.substring(start, end);
    }
  
  
negative.code:    * The format is expected to be correct.
     */
    int parseInt(int start, int end) {
      const int asciiBits = 0x7f;  // Integer literals are ASCII only.
      return int.parse(getString(start, end, asciiBits));
    }
  
    /**
  