Update existing uses of /wd4267 to use the GN config

extensions/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.
 
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//extensions/extensions.gni")
 import("//third_party/mojo/src/mojo/public/tools/bindings/mojom.gni")
 
 # GYP version: extensions/extensions.gyp:extensions_common_constants
 source_set("common_constants") {
   sources =
       rebase_path(extensions_gypi_values.extensions_common_constants_sources,
                   ".",
                   "//extensions")
-
-  if (is_win) {
-    cflags = [ "/wd4267" ]  # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
-  }
+  # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+  configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 }
 
 if (enable_extensions) {
   mojom("mojo") {
     sources = rebase_path(extensions_gypi_values.extensions_common_mojo_sources,
                           ".",
                           "//extensions")
   }
 
   # GYP version: extensions/extensions.gyp:extensions_common
   source_set("common") {
     sources = rebase_path(extensions_gypi_values.extensions_common_sources,
                           ".",
                           "//extensions")
+    # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+    configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
     deps = [
       ":common_constants",
       ":mojo",
 
       # TODO(benwells): figure out what to do with the api target and
       # api resources compiled into the chrome resource bundle.
       # http://crbug.com/162530
       "//chrome:resources",
       "//components/crx_file",
@@ skipping 30 matching lines @@
       sources += nonssl_sources
     }
 
     if (enable_nacl) {
       nacl_sources =
           rebase_path(extensions_gypi_values.extensions_common_sources_nacl,
                       ".",
                       "//extensions")
       sources += nacl_sources
     }
-
-    if (is_win) {
-      cflags = [ "/wd4267" ]  # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
-    }
   }
 }  # enable_extensions