[mojo-edk] Minor clean-up in the ports layer

mojo/edk/system/ports/BUILD.gn

 # Copyright 2016 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("//testing/test.gni")
 
 source_set("ports") {
   sources = [
+    "event.cc",
     "event.h",
     "hash_functions.h",
     "message.cc",
     "message.h",
     "message_queue.cc",
     "message_queue.h",
     "name.cc",
     "name.h",
     "node.cc",
     "node.h",
     "node_delegate.h",
     "port.cc",
     "port.h",
     "port_ref.cc",
     "user_data.h",
   ]
 
   public_deps = [
     "//base",
-    "//mojo/public/c/system",
   ]
 }
 
 test("mojo_system_ports_unittests") {
   sources = [
     "ports_unittest.cc",
   ]
 
   deps = [
     ":ports",
     "//base",
+    "//base/test:run_all_unittests",
     "//base/test:test_support",
-    "//mojo/edk/test:run_all_unittests",
     "//testing/gtest",
   ]
 }