Mark gtest and gmock as testonly in GN.

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.
   ]
 
@@ skipping 41 matching lines @@
     ]
   }
 }
 
 config("gtest_direct_config") {
   visibility = [ ":*" ]
   defines = [ "UNIT_TEST" ]
 }
 
 static_library("gtest") {
+  # TODO http://crbug.com/412064 enable this flag all the time.
+  testonly = !is_component_build
   sources = [
     "include/gtest/gtest-death-test.h",
     "include/gtest/gtest-message.h",
     "include/gtest/gtest-param-test.h",
     "include/gtest/gtest-printers.h",
     "include/gtest/gtest-spi.h",
     "include/gtest/gtest-test-part.h",
     "include/gtest/gtest-typed-test.h",
     "include/gtest/gtest.h",
     "include/gtest/gtest_pred_impl.h",
@@ skipping 32 matching lines @@
   include_dirs = [ "." ]
 
   all_dependent_configs = [ ":gtest_config" ]
   direct_dependent_configs = [ ":gtest_direct_config" ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
 }
 
 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" ]
 }