Fix some warnings.

frog/lib/string_implementation.dart

 // Copyright (c) 2011, 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.
 
 //String.prototype.get$length = function() {
 //  return this.length;
 //}
 
 // TODO(jimhug): Unify with code from compiler/lib/implementation.
 class StringImplementation implements String native "String" {
@@ skipping 73 matching lines @@
     if (pattern is RegExp) return _splitRegExp(pattern);
     throw "String.split(Pattern) unimplemented.";
   }
 
   List<String> _split(String pattern) native
     "'use strict'; return this.split(pattern);";
 
   List<String> _splitRegExp(RegExp pattern) native
     "'use strict'; return this.split(pattern.re);";
 
+  Iterable<Match> allMatches(String str) {
+    throw "String.allMatches(String str) unimplemented.";
+  }
   /*
   Iterable<Match> allMatches(String str) {
     List<Match> result = [];
     if (this.isEmpty()) return result;
     int length = this.length;
 
     int ix = 0;
     while (ix < str.length) {
       int foundIx = str.indexOf(this, ix);
       if (foundIx < 0) break;
@@ skipping 68 matching lines @@
       result.add(group(g));
     }
     return result;
   }
 
   final int _start;
   final String str;
   final String pattern;
 }
 */