Non-format-changing kernel offset changes

pkg/kernel/bin/dartk.dart

 #!/usr/bin/env dart
 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
 import 'dart:io';
 
 import 'batch_util.dart';
 
@@ skipping 57 matching lines @@
   ..addFlag('tolerant',
       help: 'Generate kernel even if there are compile-time errors.',
       defaultsTo: false)
   ..addOption('D',
       abbr: 'D',
       allowMultiple: true,
       help: 'Define an environment variable.',
       hide: true)
   ..addFlag('show-external',
       help: 'When printing a library as text, also print its dependencies\n'
-          'on external libraries.');
+          'on external libraries.')
+  ..addFlag('show-offsets',
+      help: 'When printing a library as text, also print node offsets');
 
 String getUsage() => """
 Usage: dartk [options] FILE
 
 Convert .dart or .dill files to kernel's IR and print out its textual
 or binary form.
 
 Examples:
     dartk foo.dart            # print text IR for foo.dart
     dartk foo.dart -ofoo.dill # write binary IR for foo.dart to foo.dill
@@ skipping 280 matching lines @@
     return CompilerOutcome.Ok;
   }
 
   watch.reset();
 
   Future ioFuture;
   if (canContinueCompilation) {
     switch (format) {
       case 'text':
         writeProgramToText(program,
-            path: outputFile, showExternal: options['show-external']);
+            path: outputFile,
+            showExternal: options['show-external'],
+            showOffsets: options['show-offsets']);
         break;
       case 'bin':
         ioFuture = writeProgramToBinary(program, outputFile);
         break;
     }
   }
 
   int time = watch.elapsedMilliseconds;
   if (shouldReportMetrics) {
     print('writer.time = $time ms');
   }
 
   await ioFuture;
 
   if (shouldReportMetrics) {
     int flushTime = watch.elapsedMilliseconds - time;
     print('writer.flush_time = $flushTime ms');
   }
 
   return errors.length > 0 ? CompilerOutcome.Fail : CompilerOutcome.Ok;
 }