Remove Windows-related GN build configuration

build/secondary/testing/gtest/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.
 
 config("gtest_config") {
   visibility = [
     ":*",
     "//testing/gmock:*",  # gmock also shares this config.
   ]
 
   defines = [
     # In order to allow regex matches in gtest to be shared between Windows
     # and other systems, we tell gtest to always use it's internal engine.
     "GTEST_HAS_POSIX_RE=0",
 
     # Chrome doesn't support / require C++11, yet.
     "GTEST_LANG_CXX11=0",
   ]
 
   # Gtest headers need to be able to find themselves.
   include_dirs = [ "include" ]
 
-  if (is_win) {
-    cflags = [ "/wd4800" ]  # Unused variable warning.
-  }
-
   if (is_posix) {
     defines += [
       # gtest isn't able to figure out when RTTI is disabled for gcc
       # versions older than 4.3.2, and assumes it's enabled.  Our Mac
       # and Linux builds disable RTTI, and cannot guarantee that the
       # compiler will be 4.3.2. or newer.  The Mac, for example, uses
       # 4.2.1 as that is the latest available on that platform.  gtest
       # must be instructed that RTTI is disabled here, and for any
       # direct dependents that might include gtest headers.
       "GTEST_HAS_RTTI=0",
@@ skipping 79 matching lines @@
 source_set("gtest_main") {
   # TODO http://crbug.com/412064 enable this flag all the time.
   testonly = !is_component_build
   sources = [
     "src/gtest_main.cc",
   ]
   deps = [
     ":gtest",
   ]
 }