Roll googletest to 1.8.0.

build/secondary/testing/gmock/BUILD.gn

Index: build/secondary/testing/gmock/BUILD.gn
diff --git a/build/secondary/testing/gmock/BUILD.gn b/build/secondary/testing/gmock/BUILD.gn
index c7e109d2a0b04de9a87a628a2b4c23b8ceb9a191..9184d623c822aad14c07d1b903c49afd956368b8 100644
--- a/build/secondary/testing/gmock/BUILD.gn
+++ b/build/secondary/testing/gmock/BUILD.gn
@@ -2,6 +2,13 @@
 # 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 gmock now lives at testing/gmock/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
+
 config("gmock_config") {
   # Gmock headers need to be able to find themselves.
   include_dirs = [