Inhibit title update when removing children before setting new value

Source/core/html/HTMLTitleElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2010 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #include "config.h"
 #include "core/html/HTMLTitleElement.h"
 
 #include "HTMLNames.h"
 #include "bindings/v8/ExceptionStatePlaceholder.h"
+#include "core/dom/ChildListMutationScope.h"
 #include "core/dom/Document.h"
 #include "core/dom/Text.h"
 #include "core/rendering/style/RenderStyle.h"
 #include "core/rendering/style/StyleInheritedData.h"
 #include "wtf/text/StringBuilder.h"
 
 namespace WebCore {
 
 using namespace HTMLNames;
 
 inline HTMLTitleElement::HTMLTitleElement(Document& document)
     : HTMLElement(titleTag, document)
+    , m_ignoreTitleUpdatesWhenChildrenChange(false)
 {
     setHasCustomStyleCallbacks();
     ScriptWrappable::init(this);
 }
 
 PassRefPtr<HTMLTitleElement> HTMLTitleElement::create(Document& document)
 {
     return adoptRef(new HTMLTitleElement(document));
 }
 
 Node::InsertionNotificationRequest HTMLTitleElement::insertedInto(ContainerNode* insertionPoint)
 {
     HTMLElement::insertedInto(insertionPoint);
     if (inDocument() && !isInShadowTree())
         document().setTitleElement(text(), this);
     return InsertionDone;
 }
 
 void HTMLTitleElement::removedFrom(ContainerNode* insertionPoint)
 {
     HTMLElement::removedFrom(insertionPoint);
     if (insertionPoint->inDocument() && !insertionPoint->isInShadowTree())
         document().removeTitle(this);
 }
 
 void HTMLTitleElement::childrenChanged(bool changedByParser, Node* beforeChange, Node* afterChange, int childCountDelta)
 {
     HTMLElement::childrenChanged(changedByParser, beforeChange, afterChange, childCountDelta);
-    if (inDocument() && !isInShadowTree())
+    if (inDocument() && !isInShadowTree() && !m_ignoreTitleUpdatesWhenChildrenChange)
         document().setTitleElement(text(), this);
 }
 
 String HTMLTitleElement::text() const
 {
     StringBuilder result;
 
     for (Node *n = firstChild(); n; n = n->nextSibling()) {
         if (n->isTextNode())
             result.append(toText(n)->data());
     }
 
     return result.toString();
 }
 
 void HTMLTitleElement::setText(const String &value)
 {
     RefPtr<Node> protectFromMutationEvents(this);
+    ChildListMutationScope mutation(*this);
 
-    int numChildren = childNodeCount();
+    // Avoid calling Document::setTitleElement() during intermediate steps.
+    m_ignoreTitleUpdatesWhenChildrenChange = true;
+    removeChildren();
+    m_ignoreTitleUpdatesWhenChildrenChange = false;
 
-    if (numChildren == 1 && firstChild()->isTextNode())
-        toText(firstChild())->setData(value);
-    else {
-        // We make a copy here because entity of "value" argument can be Document::m_title,
-        // which goes empty during removeChildren() invocation below,
-        // which causes HTMLTitleElement::childrenChanged(), which ends up in Document::setTitleElement().
-        String valueCopy(value);
-
-        if (numChildren > 0)
-            removeChildren();
-
-        appendChild(document().createTextNode(valueCopy.impl()), IGNORE_EXCEPTION);
-    }
+    appendChild(document().createTextNode(value.impl()), IGNORE_EXCEPTION);
 }
 
 }