Fix to WATCHLISTS.

WATCHLISTS

 # Copyright (c) 2013, 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.
 
 # Watchlist Rules
 # Refer: http://dev.chromium.org/developers/contributing-code/watchlists
 
 {
   'WATCHLIST_DEFINITIONS': {
     'runtime': {
-      'filepath': 'runtime/',
+      'filepath': '^runtime/',
     },
     'tools': {
       'filepath': 'tools/',
     },
     'observatory': {
       'filepath': 'runtime/bin/vmservice/' \
                   '|runtime/bin/vmservice*' \
                   '|runtime/observatory/' \
                   '|runtime/vm/service/' \
                   '|runtime/vm/service*'
     },
   },
 
   'WATCHLISTS': {
     'runtime': ['vm-dev@dartlang.org'],
     'tools': ['ricow@google.com'],
     'observatory': ['johnmccutchan@google.com', 'turnidge@google.com', 'rmacnak@google.com'],
   },
 }