Make mojo::system::Core not own the PlatformSupport.

mojo/edk/embedder/test_embedder.cc

 // 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.
 
 #include "mojo/edk/embedder/test_embedder.h"
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "mojo/edk/embedder/embedder.h"
@@ skipping 36 matching lines @@
 
 bool Shutdown() {
   CHECK(internal::g_channel_manager);
   delete internal::g_channel_manager;
   internal::g_channel_manager = nullptr;
 
   CHECK(internal::g_core);
   bool rv = system::internal::ShutdownCheckNoLeaks(internal::g_core);
   delete internal::g_core;
   internal::g_core = nullptr;
+
+  CHECK(internal::g_platform_support);
+  delete internal::g_platform_support;
+  internal::g_platform_support = nullptr;
+
   return rv;
 }
 
 }  // namespace test
 }  // namespace embedder
 
 }  // namespace mojo