Add a non-null check for a pointer to NPAPIClient::ExecuteGetJavascriptUrlTest::TimerProc

BUG=106522
TEST=trybot

Review URL: http://codereview.chromium.org/8817014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@114633 0039d316-1c4b-4281-b951-d872f2087c98

webkit/plugins/npapi/test/plugin_get_javascript_url_test.cc

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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 "webkit/plugins/npapi/test/plugin_get_javascript_url_test.h"
 
 #include "base/basictypes.h"
+#include "base/logging.h"
 
 // url for "self".
 #define SELF_URL "javascript:window.location+\"\""
@@ -67,6 +68,7 @@ void CALLBACK ExecuteGetJavascriptUrlTest::TimerProc(
   ExecuteGetJavascriptUrlTest* this_instance =
       reinterpret_cast<ExecuteGetJavascriptUrlTest*>
           (::GetProp(window, L"Plugin_Instance"));
+  CHECK(this_instance);
 
   ::RemoveProp(window, L"Plugin_Instance");