GN build fixes, mostly for Mac.

third_party/re2/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.
 
 # TODO(brettw) use this value when we remove external=true below.
 #gyp_file = "//$gyp_output_dir/gn_gyp/third_party/re2/re2.gyp"
 
 config("re2_config") {
   include_dirs = [ "." ]
 }
@@ skipping 53 matching lines @@
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   direct_dependent_configs = [ ":re2_config" ]
 
   deps = [
     "//base/third_party/dynamic_annotations",
   ]
 
   if (is_win) {
     include_dirs = [ "mswin" ]
-    # TODO(brettw) 'msvs_disabled_warnings': [ 4018, 4722, 4267 ],
+    cflags = [
+      "/wd4267",  # Conversion from size_t.
+      "/wd4722",  # Destructor never terminates.
+    ]
   } else {
     sources -= [ "mswin/stdint.h" ]
   }
 }