[Windows Sandbox Tests] Process Mitigations.

sandbox/win/tests/integration_tests/hooking_dll.cc

 // 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.
 
 #include <stdio.h>
 #include <windows.h>
 
-#define _DLL_EXPORTING
 #include "integration_tests_common.h"
 
 // This data section creates a common area that is accessible
 // to all instances of the DLL (in every process).  They map to
 // the same physical memory location.
 // **Note that each instance of this DLL runs in the context of
 // the process it's injected into, so things like pointers and
 // addresses won't work.
 // **Note that any variables must be initialized to put them in
 // the specified segment, otherwise they will end up in the
@@ skipping 28 matching lines @@
   // but I'm doing it here to show the shared use of the HHOOK variable in
   // the shared data segment.  It is set by the instance of the DLL in the
   // main test process.
   return CallNextHookEx(hook, code, w_param, l_param);
 }
 
 BOOL WINAPI DllMain(HINSTANCE instance, DWORD reason, LPVOID reserved) {
   if (reason == DLL_PROCESS_ATTACH) {
     // The testing process should have set up this named event already
     // (if the test needs this event to be signaled).
-    event = ::OpenEventW(EVENT_MODIFY_STATE, FALSE, g_hook_event);
+    event = ::OpenEventW(EVENT_MODIFY_STATE, FALSE, sandbox::g_hook_event);
   }
 
-  if (reason == DLL_PROCESS_DETACH)
+  if (reason == DLL_PROCESS_DETACH && event != nullptr)
     ::CloseHandle(event);
 
   return TRUE;
 }