Update dpranke's entry in the WATCHLISTS.

WATCHLISTS

 # Copyright (c) 2012 The Chromium Authors. 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': {
     'this_file': {
       'filepath': '^WATCHLISTS$',
     },
     'depot_tools': {
       'filepath': '.+',
     },
   },
 
   'WATCHLISTS': {
     'this_file': [],
     'depot_tools': [
       'cmp-cc@chromium.org',
-      'dpranke@chromium.org',
+      'dpranke+depot_tools@chromium.org',
       'iannucci+depot_tools@chromium.org',
     ],
   },
 
 }