Pepper: CallOnMainThread should do nothing if Globals are gone

ppapi/proxy/ppb_core_proxy.cc

 // Copyright (c) 2012 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 "ppapi/proxy/ppb_core_proxy.h"
 
 #include <stdlib.h>  // For malloc
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ skipping 45 matching lines @@
   DCHECK(callback.func);
 #if defined(OS_NACL)
   // Some NaCl apps pass a negative delay, so we just sanitize to 0, to run as
   // soon as possible. MessageLoop checks that the delay is non-negative.
   if (delay_in_ms < 0)
     delay_in_ms = 0;
 #endif
   if (!callback.func)
     return;
   ProxyAutoLock lock;
+
+  // If the plugin attempts to call CallOnMainThread from a background thread
+  // at shutdown, it's possible that the PpapiGlobals object or the main loop
+  // has been destroyed.
+  if (!PpapiGlobals::Get() || !PpapiGlobals::Get()->GetMainThreadMessageLoop())
+    return;
+
   PpapiGlobals::Get()->GetMainThreadMessageLoop()->PostDelayedTask(
       FROM_HERE,
       RunWhileLocked(base::Bind(&CallbackWrapper, callback, result)),
       base::TimeDelta::FromMilliseconds(delay_in_ms));
 }
 
 PP_Bool IsMainThread() {
   return PP_FromBool(PpapiGlobals::Get()->
       GetMainThreadMessageLoop()->BelongsToCurrentThread());
 }
@@ skipping 48 matching lines @@
   ppb_core_impl_->AddRefResource(resource.host_resource());
 }
 
 void PPB_Core_Proxy::OnMsgReleaseResource(const HostResource& resource) {
   ppb_core_impl_->ReleaseResource(resource.host_resource());
 }
 #endif  // !defined(OS_NACL)
 
 }  // namespace proxy
 }  // namespace ppapi