Revert of Convert the re2 GYP targets to be generated by GN.

tools/gn/secondary/third_party/re2/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("re2_config") {
+  include_dirs = [ "." ]
+}
+
+gyp_file = "re2.gyp"
+external = true
+
+static_library("re2") {
+  sources = [
+    "mswin/stdint.h",
+    "re2/bitstate.cc",
+    "re2/compile.cc",
+    "re2/dfa.cc",
+    "re2/filtered_re2.cc",
+    "re2/filtered_re2.h",
+    "re2/mimics_pcre.cc",
+    "re2/nfa.cc",
+    "re2/onepass.cc",
+    "re2/parse.cc",
+    "re2/perl_groups.cc",
+    "re2/prefilter.cc",
+    "re2/prefilter.h",
+    "re2/prefilter_tree.cc",
+    "re2/prefilter_tree.h",
+    "re2/prog.cc",
+    "re2/prog.h",
+    "re2/re2.cc",
+    "re2/re2.h",
+    "re2/regexp.cc",
+    "re2/regexp.h",
+    "re2/set.cc",
+    "re2/set.h",
+    "re2/simplify.cc",
+    "re2/stringpiece.h",
+    "re2/tostring.cc",
+    "re2/unicode_casefold.cc",
+    "re2/unicode_casefold.h",
+    "re2/unicode_groups.cc",
+    "re2/unicode_groups.h",
+    "re2/variadic_function.h",
+    "re2/walker-inl.h",
+    "util/arena.cc",
+    "util/arena.h",
+    "util/atomicops.h",
+    "util/flags.h",
+    "util/hash.cc",
+    "util/logging.h",
+    "util/mutex.h",
+    "util/rune.cc",
+    "util/sparse_array.h",
+    "util/sparse_set.h",
+    "util/stringpiece.cc",
+    "util/stringprintf.cc",
+    "util/strutil.cc",
+    "util/utf.h",
+    "util/util.h",
+  ]
+
+  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 ],
+  } else {
+    sources -= "mswin/stdint.h"
+  }
+}