Remove custom gmock-port.h.

It works around a problem that is not applicable to Chromium.

Change-Id: I8eaaf8ed1340e9892461e89535b3d896c822ce0b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2369504
Commit-Queue: Victor Costan <pwnall@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800817}

third_party/googletest/BUILD.gn

@@ -172,9 +172,6 @@ source_set("gmock") {
     "src/googlemock/include/gmock/internal/gmock-port.h",
     "src/googlemock/include/gmock/internal/gmock-pp.h",
 
-    # gmock helpers.
-    "custom/gmock/internal/custom/gmock-port.h",
-
     #"src/googlemock/src/gmock-all.cc",  # Not needed by our build.
     "src/googlemock/src/gmock-cardinalities.cc",
     "src/googlemock/src/gmock-internal-utils.cc",

third_party/googletest/custom/gmock/internal/custom/gmock-port.h

-// Copyright 2016 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.
-
-#ifndef THIRD_PARTY_GOOGLETEST_CUSTOM_GMOCK_INTERNAL_CUSTOM_GMOCK_PORT_H_
-#define THIRD_PARTY_GOOGLETEST_CUSTOM_GMOCK_INTERNAL_CUSTOM_GMOCK_PORT_H_
-
-#include <type_traits>
-
-namespace std {
-
-// Provide alternative implementation of std::is_default_constructible for
-// old, pre-4.7 of libstdc++, where is_default_constructible is missing.
-// <20120322 below implies pre-4.7.0. In addition we blacklist several version
-// that released after 4.7.0 from pre-4.7.0 branch. 20120702 implies 4.5.4, and
-// 20121127 implies 4.6.4.
-#if defined(__GLIBCXX__) &&                               \
-    (__GLIBCXX__ < 20120322 || __GLIBCXX__ == 20120702 || \
-     __GLIBCXX__ == 20121127)
-template <typename T>
-using is_default_constructible = std::is_constructible<T>;
-#endif
-}
-
-#endif  // THIRD_PARTY_GOOGLETEST_CUSTOM_GMOCK_INTERNAL_CUSTOM_GMOCK_PORT_H_