Measure how often Attr needs its associated Element

Source/core/dom/Attr.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2009, 2010, 2012 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
@@ skipping 10 matching lines @@
  * Boston, MA 02110-1301, USA.
  */
 #include "config.h"
 #include "core/dom/Attr.h"
 
 #include "bindings/v8/ExceptionState.h"
 #include "bindings/v8/ExceptionStatePlaceholder.h"
 #include "core/dom/Element.h"
 #include "core/dom/Text.h"
 #include "core/events/ScopedEventQueue.h"
+#include "core/frame/UseCounter.h"
 #include "wtf/text/AtomicString.h"
 #include "wtf/text/StringBuilder.h"
 
 namespace WebCore {
 
 using namespace HTMLNames;
 
 Attr::Attr(Element& element, const QualifiedName& name)
     : ContainerNode(&element.document())
     , m_element(&element)
     , m_name(name)
     , m_ignoreChildrenChanged(0)
 {
     ScriptWrappable::init(this);
+    m_standaloneValue = value();
 }
 
 Attr::Attr(Document& document, const QualifiedName& name, const AtomicString& standaloneValue)
     : ContainerNode(&document)
     , m_element(0)
     , m_name(name)
     , m_standaloneValue(standaloneValue)
     , m_ignoreChildrenChanged(0)
 {
     ScriptWrappable::init(this);
@@ skipping 32 matching lines @@
     }
 }
 
 void Attr::setValue(const AtomicString& value)
 {
     EventQueueScope scope;
     m_ignoreChildrenChanged++;
     removeChildren();
     if (m_element)
         elementAttribute().setValue(value);
-    else
-        m_standaloneValue = value;
+    m_standaloneValue = value;
     createTextChild();
     m_ignoreChildrenChanged--;
 
     invalidateNodeListCachesInAncestors(&m_name, m_element);
 }
 
 void Attr::setValue(const AtomicString& value, ExceptionState&)
 {
     if (m_element)
         m_element->willModifyAttribute(qualifiedName(), this->value(), value);
 
     setValue(value);
 
     if (m_element)
         m_element->didModifyAttribute(qualifiedName(), value);
 }
 
+const AtomicString& Attr::valueForBindings() const
+{
+    if (m_element && m_standaloneValue != value())
+        UseCounter::count(document(), UseCounter::AttrGetValueNeedsElement);
+    return value();
+}
+
+void Attr::setValueForBindings(const AtomicString& value)
+{
+    if (m_element && value != this->value())
+        UseCounter::count(document(), UseCounter::AttrSetValueNeedsElement);
+    setValue(value, IGNORE_EXCEPTION);
+}
+
 void Attr::setNodeValue(const String& v)
 {
     // Attr uses AtomicString type for its value to save memory as there
     // is duplication among Elements' attributes values.
     setValue(AtomicString(v), IGNORE_EXCEPTION);
 }
 
 PassRefPtr<Node> Attr::cloneNode(bool /*deep*/)
 {
     RefPtr<Attr> clone = adoptRef(new Attr(document(), qualifiedName(), value()));
     cloneChildNodes(clone.get());
     return clone.release();
 }
 
 // DOM Section 1.1.1
 bool Attr::childTypeAllowed(NodeType type) const
 {
     return TEXT_NODE == type;
 }
 
 void Attr::childrenChanged(bool, Node*, Node*, int)
 {
     if (m_ignoreChildrenChanged > 0)
         return;
 
+    UseCounter::count(document(), UseCounter::AttrChildrenChanged);
+
     invalidateNodeListCachesInAncestors(&qualifiedName(), m_element);
 
     StringBuilder valueBuilder;
     for (Node *n = firstChild(); n; n = n->nextSibling()) {
         if (n->isTextNode())
             valueBuilder.append(toText(n)->data());
     }
 
     AtomicString newValue = valueBuilder.toAtomicString();
     if (m_element)
         m_element->willModifyAttribute(qualifiedName(), value(), newValue);
 
     if (m_element)
         elementAttribute().setValue(newValue);
-    else
-        m_standaloneValue = newValue;
+    m_standaloneValue = newValue;
 
     if (m_element)
         m_element->attributeChanged(qualifiedName(), newValue);
 }
 
 const AtomicString& Attr::value() const
 {
     if (m_element)
         return m_element->getAttribute(qualifiedName());
     return m_standaloneValue;
 }
 
 Attribute& Attr::elementAttribute()
 {
     ASSERT(m_element);
     ASSERT(m_element->elementData());
     return *m_element->ensureUniqueElementData().getAttributeItem(qualifiedName());
 }
 
 void Attr::detachFromElementWithValue(const AtomicString& value)
 {
     ASSERT(m_element);
-    ASSERT(m_standaloneValue.isNull());
     m_standaloneValue = value;
     m_element = 0;
 }
 
 void Attr::attachToElement(Element* element)
 {
     ASSERT(!m_element);
     m_element = element;
-    m_standaloneValue = nullAtom;
+    m_standaloneValue = value();
 }
 
 }