anchor.diff:        : this(value: value, direction: AlignmentDirection.Center);
   
     String render(int width) {
  +    if (value.length > width) {
  +      // Narrowed column.
  +      return value.substring(0, width - 2) + '..';
  +    }
       switch (direction) {
         case AlignmentDirection.Left:
           return value.padRight(width);
  
positive.code: import 'dart:io';
  import 'dart:math' as math;
  
  void main(List<String> args) {
    if (args.length != 2) {
      print("""
  Usage: dart ${Platform.script} <old.json> <new.json>
  
  This tool compares two JSON size reports produced by
  --print-instructions-sizes-to and reports which symbols increased in size
  and which symbols decreased in size.
  """);
      exit(-1);
    }
  
negative.code:       }
      }
  
      if (limitWidth) {
        for (var i = 0; i < widths.length; i++) {
          widths[i] = math.min(widths[i], 25);
        }
      }
  
      for (var row in rows) {
        print(row.render(widths, alignments));
      }
  