Roll googletest to 1.8.0.

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.
 
+# Chromium's GN configuration for gtest now lives at testing/gtest/BUILD.gn.
+#
+# This configuration is left in the tree because it is pulled by V8 and PDFium,
+# and will be removed as soon as the projects switch off of it.
+#
+# Details at http://crbug.com/630705 and http://crrev.com/2779193002
+
 import("//build_overrides/gtest.gni")
 
 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
@@ skipping 106 matching lines @@
 
 source_set("gtest_main") {
   testonly = true
   sources = [
     "src/gtest_main.cc",
   ]
   deps = [
     ":gtest",
   ]
 }