nacl_loader_unittests should be a test target.

components/nacl/BUILD.gn

 # Copyright (c) 2015 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("//build/config/features.gni")
 import("//build/config/ui.gni")
+import("//testing/test.gni")
 
 if (enable_nacl) {
   source_set("nacl") {
     sources = [
       "loader/nacl_ipc_adapter.cc",
       "loader/nacl_ipc_adapter.h",
       "loader/nacl_listener.cc",
       "loader/nacl_listener.h",
       "loader/nacl_main.cc",
       "loader/nacl_main_platform_delegate.h",
@@ skipping 102 matching lines @@
 
     deps = [
       ":nacl_common",
       "renderer/plugin:nacl_trusted_plugin",
       "//content/public/renderer",
       "//third_party/jsoncpp",
       "//third_party/WebKit/public:blink",
     ]
   }
 
-  executable("nacl_loader_unittests") {
-    testonly = true
+  test("nacl_loader_unittests") {
     sources = [
       "loader/run_all_unittests.cc",
     ]
 
     deps = [
       ":nacl",
       "//base/test:test_support",
       "//testing/gtest",
     ]
   }
@@ skipping 118 matching lines @@
 
   if (is_linux) {
     sources += [
       "common/nacl_paths.cc",
       "common/nacl_paths.h",
     ]
 
     defines = [ "__STDC_LIMIT_MACROS=1" ]
   }
 }