Fix broken assertion.

dart/lib/compiler/implementation/dart2js.dart

 // Copyright (c) 2012, 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.
 
 #library('dart2js');
 
 #import('dart:io');
 #import('dart:uri');
 #import('dart:utf');
 
@@ skipping 17 matching lines @@
 String extractParameter(String argument) {
   return argument.substring(argument.indexOf('=') + 1);
 }
 
 void parseCommandLine(List<OptionHandler> handlers, List<String> argv) {
   var patterns = <String>[];
   for (OptionHandler handler in handlers) {
     patterns.add(handler.pattern);
   }
   var pattern = new RegExp('^(${Strings.join(patterns, ")|(")})\$');
-  assert(pattern.groupCount() == handlers.length);
   OUTER: for (String argument in argv) {
     Match match = pattern.firstMatch(argument);
+    assert(match.groupCount() == handlers.length);
     for (int i = 0; i < handlers.length; i++) {
       if (match[i + 1] !== null) {
         handlers[i].handle(argument);
         continue OUTER;
       }
     }
     throw 'Internal error: "$argument" did not match';
   }
 }
 
@@ skipping 172 matching lines @@
     } catch (var ignored) {
       print('Internal error: error while printing exception');
     }
     try {
       print(trace);
     } finally {
       exit(253); // 253 is recognized as a crash by our test scripts.
     }
   }
 }