Don't queue mutation records when attributes don't change value.

sky/engine/core/dom/Element.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)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 614 matching lines @@
     }
 
     if (index == kNotFound) {
         appendAttributeInternal(name, newValue, inSynchronizationOfLazyAttribute);
         return;
     }
 
     const Attribute& existingAttribute = elementData()->attributes().at(index);
     QualifiedName existingAttributeName = existingAttribute.name();
 
+    if (newValue == existingAttribute.value())
+        return;
+
     if (!inSynchronizationOfLazyAttribute)
         willModifyAttribute(existingAttributeName, existingAttribute.value(), newValue);
 
-    if (newValue != existingAttribute.value())
-        ensureUniqueElementData().attributes().at(index).setValue(newValue);
+    ensureUniqueElementData().attributes().at(index).setValue(newValue);
 
     if (!inSynchronizationOfLazyAttribute)
         attributeChanged(existingAttributeName, newValue);
 }
 
 void Element::attributeChanged(const QualifiedName& name, const AtomicString& newValue, AttributeModificationReason reason)
 {
     if (ElementShadow* parentElementShadow = shadowWhereNodeCanBeDistributed(*this)) {
         if (shouldInvalidateDistributionWhenAttributeChanged(parentElementShadow, name, newValue))
             parentElementShadow->setNeedsDistributionRecalc();
@@ skipping 874 matching lines @@
     ASSERT(oldId != newId);
 
     if (!oldId.isEmpty())
         scope.removeElementById(oldId, this);
     if (!newId.isEmpty())
         scope.addElementById(newId, this);
 }
 
 void Element::willModifyAttribute(const QualifiedName& name, const AtomicString& oldValue, const AtomicString& newValue)
 {
-    if (name == HTMLNames::idAttr) {
+    if (name == HTMLNames::idAttr)
         updateId(oldValue, newValue);
-    }
 
-    if (oldValue != newValue) {
-        if (inActiveDocument() && styleChangeType() < SubtreeStyleChange && affectedByAttributeSelector(name.localName()))
-            setNeedsStyleRecalc(LocalStyleChange);
+    if (inActiveDocument() && styleChangeType() < SubtreeStyleChange && affectedByAttributeSelector(name.localName()))
+        setNeedsStyleRecalc(LocalStyleChange);
 
-        if (isUpgradedCustomElement())
-            CustomElement::attributeDidChange(this, name.localName(), oldValue, newValue);
-    }
+    if (isUpgradedCustomElement())
+        CustomElement::attributeDidChange(this, name.localName(), oldValue, newValue);
 
     if (OwnPtr<MutationObserverInterestGroup> recipients = MutationObserverInterestGroup::createForAttributesMutation(*this, name))
         recipients->enqueueMutationRecord(MutationRecord::createAttributes(this, name, oldValue));
 }
 
 static bool needsURLResolutionForInlineStyle(const Element& element, const Document& oldDocument, const Document& newDocument)
 {
     if (oldDocument == newDocument)
         return false;
     if (oldDocument.baseURL() == newDocument.baseURL())
@@ skipping 277 matching lines @@
         return false;
     if (treeScope().scopedStyleResolver().features().hasSelectorForId(idValue))
         return true;
     // Host rules could also have effects.
     if (ShadowRoot* shadowRoot = this->shadowRoot())
         return shadowRoot->scopedStyleResolver().features().hasSelectorForId(idValue);
     return false;
 }
 
 } // namespace blink