Make app_list tests build on Win64

ui/app_list/app_list.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 145 matching lines @@
               # Needed to link to Obj-C static libraries.
               'xcode_settings': {'OTHER_LDFLAGS': ['-Wl,-ObjC']},
             }],
           ],
         }, {  # OS!="mac"
           'sources/': [
             ['exclude', 'cocoa/'],
           ],
         }],
       ],
+      # Disable c4267 warnings until we fix size_t to int truncations.
+      'msvs_disabled_warnings': [ 4267, ],
     },
   ],
 }