Update existing uses of /wd4267 to use the GN config

storage/common/BUILD.gn

 # Copyright 2014 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.
 
 # GYP version: storage/storage_common.gyp:storage_common
 component("common") {
   output_name = "storage_common"
   sources = [
     "data_element.cc",
     "data_element.h",
     "storage_common_export.h",
     "database/database_connections.cc",
     "database/database_connections.h",
     "database/database_identifier.cc",
     "database/database_identifier.h",
     "fileapi/directory_entry.cc",
     "fileapi/directory_entry.h",
     "fileapi/file_system_info.cc",
     "fileapi/file_system_info.h",
     "fileapi/file_system_mount_option.h",
     "fileapi/file_system_types.h",
     "fileapi/file_system_util.cc",
     "fileapi/file_system_util.h",
     "quota/quota_status_code.cc",
     "quota/quota_status_code.h",
     "quota/quota_types.h",
   ]
 
+  # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+  configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
+
   defines = [ "STORAGE_COMMON_IMPLEMENTATION" ]
-  if (is_win) {
-    cflags = [ "/wd4267" ]  # TODO(jschuh): fix size_t to int truncations.
-  }
 
   deps = [
     "//base",
     "//base/third_party/dynamic_annotations",
     "//net",
     "//url",
   ]
 }