Inhibit title update when removing children before setting new value

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 1288 matching lines @@
     m_titleSetExplicitly = true;
     if (!isHTMLDocument() && !isXHTMLDocument())
         m_titleElement = 0;
     else if (!m_titleElement) {
         if (HTMLElement* headElement = head()) {
             m_titleElement = createElement(titleTag, false);
             headElement->appendChild(m_titleElement);
         }
     }
 
-    if (m_titleElement)
+    if (m_titleElement && m_titleElement->hasTagName(titleTag)) {
+        IgnoreTitleUpdatesWhenChildrenChange inhibitor(toHTMLTitleElement(m_titleElement));
         m_titleElement->removeChildren();
+    }
 
     updateTitle(title);
 
     if (m_titleElement && m_titleElement->hasTagName(titleTag))
         toHTMLTitleElement(m_titleElement)->setText(title);

[jochen (gone - plz use gerrit), 2014/01/09 12:17:33]

since setText() will also remove the children, what about using

if (m_titleElement && ...)
  toHTMLTitleElement(...)->setText()
else
  updateTitle()

and remove the removeChildren() call above?

[davve, 2014/01/09 12:31:00]

setText() will only remove the children when !(numChildren == 1 &&
firstChild()->isTextNode()). This is a current bug according to current spec
(shared with Firefox. I filed
https://www.w3.org/Bugs/Public/show_bug.cgi?id=24240 to test whether we should
change the spec or the browsers).

Now that I actually put it in writing it feels obvious that we should (try to)
fix both bugs by aligning the code according to your suggestion. Thanks for the
sanity.

 }
 
 void Document::setTitleElement(const String& title, Element* titleElement)
 {
     if (titleElement != m_titleElement) {
         if (m_titleElement || m_titleSetExplicitly)
             // Only allow the first title element to change the title -- others have no effect.
             return;
         m_titleElement = titleElement;
     }
@@ skipping 3941 matching lines @@
 }
 
 FastTextAutosizer* Document::fastTextAutosizer()
 {
     if (!m_fastTextAutosizer && RuntimeEnabledFeatures::fastTextAutosizingEnabled())
         m_fastTextAutosizer = FastTextAutosizer::create(this);
     return m_fastTextAutosizer.get();
 }
 
 } // namespace WebCore