A focused element should lose focus when it becomes unfocusable.

Source/core/dom/Document.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, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 366 matching lines @@
 static void printNavigationErrorMessage(Frame* frame, const KURL& activeURL, const char* reason)
 {
     String message = "Unsafe JavaScript attempt to initiate navigation for frame with URL '" + frame->document()->url().string() + "' from frame with URL '" + activeURL.string() + "'. " + reason + "\n";
 
     // FIXME: should we print to the console of the document performing the navigation instead?
     frame->document()->domWindow()->printErrorMessage(message);
 }
 
 uint64_t Document::s_globalTreeVersion = 0;
 
+// This class should be passed only to Document::postTask.
+class FocusedNodeChecker: public ScriptExecutionContext::Task {

[esprehn, 2013/05/20 22:03:44]

Missing a space before : and this should be FINAL

[tkent, 2013/05/20 22:29:45]

Done.

+public:
+    static PassOwnPtr<FocusedNodeChecker> create()
+    {
+        return adoptPtr(new FocusedNodeChecker());
+    }
+    virtual ~FocusedNodeChecker() { }
+
+private:
+    FocusedNodeChecker() { }

[esprehn, 2013/05/20 22:03:44]

It be nicer if this was called CheckFocusedNodeTask or something of that nature.

[tkent, 2013/05/20 22:29:45]

Done.

+    virtual void performTask(ScriptExecutionContext* context) OVERRIDE
+    {
+        ASSERT(context->isDocument());
+        Document* document = toDocument(context);
+        document->didRunFocusedNodeCheker();
+        if (document->focusedNode() && !document->focusedNode()->isFocusable())
+            document->setFocusedNode(0);
+    }
+};
+
 Document::Document(Frame* frame, const KURL& url, bool isXHTML, bool isHTML)
     : ContainerNode(0, CreateDocument)
     , TreeScope(this)
     , m_styleResolverThrowawayTimer(this, &Document::styleResolverThrowawayTimerFired)
     , m_lastStyleResolverAccessTime(0)
     , m_activeParserCount(0)
     , m_contextFeatures(ContextFeatures::defaultSwitch())
     , m_compatibilityMode(NoQuirksMode)
     , m_compatibilityModeLocked(false)
+    , m_didPostFocusedNodeChecker(false)
     , m_domTreeVersion(++s_globalTreeVersion)
     , m_mutationObserverTypes(0)
     , m_styleSheetCollection(DocumentStyleSheetCollection::create(this))
     , m_visitedLinkState(VisitedLinkState::create(this))
     , m_readyState(Complete)
     , m_styleRecalcTimer(this, &Document::styleRecalcTimerFired)
     , m_pendingStyleRecalcShouldForce(false)
     , m_frameElementsShouldIgnoreScrolling(false)
     , m_containsValidityStyleRules(false)
     , m_updateFocusAppearanceRestoresSelection(false)
@@ skipping 1395 matching lines @@
     if (Element* oe = ownerElement())
         oe->document()->updateLayout();
 
     updateStyleIfNeeded();
 
     StackStats::LayoutCheckPoint layoutCheckPoint;
 
     // Only do a layout if changes have occurred that make it necessary.      
     if (frameView && renderer() && (frameView->layoutPending() || renderer()->needsLayout()))
         frameView->layout();
+
+    if (m_focusedNode && !m_didPostFocusedNodeChecker) {
+        postTask(FocusedNodeChecker::create());
+        m_didPostFocusedNodeChecker = true;
+    }
 }
 
 // FIXME: This is a bad idea and needs to be removed eventually.
 // Other browsers load stylesheets before they continue parsing the web page.
 // Since we don't, we can run JavaScript code that needs answers before the
 // stylesheets are loaded. Doing a layout ignoring the pending stylesheets
 // lets us get reasonable answers. The long term solution to this problem is
 // to instead suspend JavaScript execution.
 void Document::updateLayoutIgnorePendingStylesheets()
 {
@@ skipping 4069 matching lines @@
         return;
 
     Vector<RefPtr<Element> > associatedFormControls;
     copyToVector(m_associatedFormControls, associatedFormControls);
 
     frame()->page()->chrome()->client()->didAssociateFormControls(associatedFormControls);
     m_associatedFormControls.clear();
 }
 
 } // namespace WebCore