- Address warnings about 64-bit to 32-bit conversions.

tools/gyp/configurations_xcode.gypi

 # 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.
 
 # The purpose of this file and others in this directory is to simulate
 # the Chromium build enviroment. This file is included in all GYP
 # files that are used by the Dart project.
 
 # READ BEFORE EDITING:
 # Do not add Dart VM specific configuration to this file. Instead,
@@ skipping 16 matching lines @@
           'GCC_GENERATE_DEBUGGING_SYMBOLS': 'YES', # Do not strip symbols
           'GCC_SYMBOLS_PRIVATE_EXTERN': 'YES', # -fvisibility=hidden
           'GCC_INLINES_ARE_PRIVATE_EXTERN': 'YES', # -fvisibility-inlines-hidden
           'GCC_WARN_NON_VIRTUAL_DESTRUCTOR': 'YES', # -Wnon-virtual-dtor
           'GCC_TREAT_WARNINGS_AS_ERRORS': 'YES', # -Werror
           'WARNING_CFLAGS': [
             '<@(common_gcc_warning_flags)',
             '-Wtrigraphs', # Disable Xcode default.
             '-Wreturn-type',
             '-Werror=return-type',
+            # TODO(15922): Enable this flag by default.
+            # '-Wshorten-64-to-32',
           ],
 
           # Generate PIC code as Chrome is switching to this.
           'GCC_DYNAMIC_NO_PIC': 'NO',
 
           # When searching for header files, do not search
           # subdirectories. Without this option, vm/assert.h conflicts
           # with the system header assert.h. Apple also recommend
           # setting this to NO.
           'ALWAYS_SEARCH_USER_PATHS': 'NO',
@@ skipping 20 matching lines @@
       },
       'Dart_Macos_Debug': {
         'abstract': 1,
       },
       'Dart_Macos_Release': {
         'abstract': 1,
       },
     },
   },
 }