HTMLImportsController does not need to hold Document ptr.

Source/core/dom/DocumentInit.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
@@ skipping 86 matching lines @@
 bool DocumentInit::shouldTreatURLAsSrcdocDocument() const
 {
     return m_parent && m_frame->loader().shouldTreatURLAsSrcdocDocument(m_url);
 }
 
 LocalFrame* DocumentInit::frameForSecurityContext() const
 {
     if (m_frame)
         return m_frame;
     if (m_importsController)
-        return m_importsController->frame();
+        return m_importsController->master()->frame();
     return 0;
 }
 
 SandboxFlags DocumentInit::sandboxFlags() const
 {
     ASSERT(frameForSecurityContext());
     return frameForSecurityContext()->loader().effectiveSandboxFlags();
 }
 
 Settings* DocumentInit::settings() const
@@ skipping 37 matching lines @@
     return m_contextDocument;
 }
 
 DocumentInit DocumentInit::fromContext(WeakPtr<Document> contextDocument, const KURL& url)
 {
     return DocumentInit(url, 0, contextDocument, 0);
 }
 
 } // namespace WebCore