GN: Replace Windows suppressions of warning 4267 with config.

webrtc/modules/rtp_rtcp/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("../../build/webrtc.gni")
 
@@ skipping 153 matching lines @@
     # See http://code.google.com/p/webrtc/issues/detail?id=163 for details.
     configs -= [ "//build/config/clang:find_bad_constructs" ]
   }
 
   deps = [
     "../..:webrtc_common",
     "../../system_wrappers",
     "../remote_bitrate_estimator",
   ]
 
+  # TODO(jschuh): Bug 1348: fix this warning.
+  configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
+
   if (is_win) {
     cflags = [
-      # TODO(jschuh): Bug 1348: fix this warning.
-      "/wd4267",  # size_t to int truncations
-
       # TODO(kjellander): Bug 261: fix this warning.
       "/wd4373",  # virtual function override.
     ]
   }
 }