Add lots of testonly annotations to the GN build.

dbus/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.
 
 import("//third_party/protobuf/proto_library.gni")
 
 component("dbus") {
   sources = [
     "bus.cc",
     "bus.h",
@@ skipping 37 matching lines @@
   ]
 }
 
 proto_library("test_proto") {
   sources = [ "test_proto.proto" ]
 }
 
 # This target contains mocks that can be used to write unit tests without
 # issuing actual D-Bus calls.
 source_set("test_support") {
+  testonly = true
   sources = [
     "mock_bus.cc",
     "mock_bus.h",
     "mock_exported_object.cc",
     "mock_exported_object.h",
     "mock_object_manager.cc",
     "mock_object_manager.h",
     "mock_object_proxy.cc",
     "mock_object_proxy.h",
   ]
@@ skipping 36 matching lines @@
     "//testing/gtest",
     "//third_party/protobuf:protobuf_lite",
   ]
 
   configs += [
     "//build/config/linux:dbus",
   ]
 }
 
 executable("dbus_test_server") {
+  testonly = true
   sources = [
     "test_server.cc",
     "test_service.cc",
     "test_service.h",
   ]
 
   deps = [
     ":dbus",
     "//base",
     "//base/test:test_support",
   ]
 
   configs += [
     "//build/config/linux:dbus",
   ]
 }