Work on Mac GN build

tools/gn/secondary/third_party/snappy/BUILD.gn

 # Copyright (c) 2013 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.
 
 config("snappy_config") {
   include_dirs = [
     "src",
   ]
 
   # These OS-specific generated headers were made by running the configure
@@ skipping 15 matching lines @@
     "src/snappy-stubs-internal.cc",
     "src/snappy-stubs-internal.h",
     "src/snappy.cc",
     "src/snappy.h",
   ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   direct_dependent_configs = [ ":snappy_config" ]
 
-  #['OS=="win"', {
-  #          # Signed/unsigned comparison
-  #          'msvs_disabled_warnings': [
-  #            # https://code.google.com/p/snappy/issues/detail?id=71
-  #            4018,
-  #            # https://code.google.com/p/snappy/issues/detail?id=75
-  #            4267,
-  #          ],
-  #        }],
-  #      ['clang == 1', {
-  #          # snappy-stubs-internal.h unapologetically has: using namespace std
-  #          # https://code.google.com/p/snappy/issues/detail?id=70
-  #          'xcode_settings': {
-  #            'WARNING_CFLAGS!': [ '-Wheader-hygiene' ],
-  #          },
-  #          'cflags!': [ '-Wheader-hygiene' ],
-  #        }],
-  #    ],
+  if (is_clang) {
+    # snappy-stubs-internal.h unapologetically has: using namespace std
+    # https://code.google.com/p/snappy/issues/detail?id=70
+    configs -= [ "//build/config/clang:extra_warnings" ]
+  }
+
+  if (is_win) {
+    # https://code.google.com/p/snappy/issues/detail?id=75
+    cflags = [ "/wd4267" ]  # Conversion from size_t to 'type'.
+  }
 }