A focused element should lose focus when it becomes unfocusable.

Source/core/dom/Document.h

 /*
  * 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) 2011 Google Inc. All rights reserved.
  *
@@ skipping 618 matching lines @@
        spec matures. - dwh
     */
     String preferredStylesheetSet() const;
     String selectedStylesheetSet() const;
     void setSelectedStylesheetSet(const String&);
 
     bool setFocusedNode(PassRefPtr<Node>, FocusDirection = FocusDirectionNone);
     Node* focusedNode() const { return m_focusedNode.get(); }
     UserActionElementSet& userActionElements()  { return m_userActionElements; }
     const UserActionElementSet& userActionElements() const { return m_userActionElements; }
-
+    void didRunCheckFocusedNodeTask() { m_didPostCheckFocusedNodeTask = false; }
     void getFocusableNodes(Vector<RefPtr<Node> >&);
     
     // The m_ignoreAutofocus flag specifies whether or not the document has been changed by the user enough 
     // for WebCore to ignore the autofocus attribute on any form controls
     bool ignoreAutofocus() const { return m_ignoreAutofocus; };
     void setIgnoreAutofocus(bool shouldIgnore = true) { m_ignoreAutofocus = shouldIgnore; };
 
     void setHoverNode(PassRefPtr<Node>);
     Node* hoverNode() const { return m_hoverNode.get(); }
 
@@ skipping 582 matching lines @@
     bool m_printing;
     bool m_paginatedForScreen;
 
     bool m_ignoreAutofocus;
 
     CompatibilityMode m_compatibilityMode;
     bool m_compatibilityModeLocked; // This is cheaper than making setCompatibilityMode virtual.
 
     Color m_textColor;
 
+    bool m_didPostCheckFocusedNodeTask;
     RefPtr<Node> m_focusedNode;
     RefPtr<Node> m_hoverNode;
     RefPtr<Element> m_activeElement;
     RefPtr<Element> m_documentElement;
     UserActionElementSet m_userActionElements;
 
     uint64_t m_domTreeVersion;
     static uint64_t s_globalTreeVersion;
     
     HashSet<NodeIterator*> m_nodeIterators;
@@ skipping 253 matching lines @@
     trackForDebugging();
 #endif
     InspectorCounters::incrementCounter(InspectorCounters::NodeCounter);
 }
 
 Node* eventTargetNodeForDocument(Document*);
 
 } // namespace WebCore
 
 #endif // Document_h