Add iterator object to iterate efficiently over an Element's attributes

Source/core/dom/PresentationAttributeStyle.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 105 matching lines @@
 }
 
 static void makePresentationAttributeCacheKey(Element& element, PresentationAttributeCacheKey& result)
 {
     // FIXME: Enable for SVG.
     if (!element.isHTMLElement())
         return;
     // Interpretation of the size attributes on <input> depends on the type attribute.
     if (isHTMLInputElement(element))
         return;
-    unsigned size = element.attributeCount();
-    for (unsigned i = 0; i < size; ++i) {
-        const Attribute& attribute = element.attributeItem(i);
-        if (!element.isPresentationAttribute(attribute.name()))
+    AttributeIteratorAccessor attributes = element.attributesIterator();
+    AttributeConstIterator end = attributes.end();
+    for (AttributeConstIterator it = attributes.begin(); it != end; ++it) {
+        if (!element.isPresentationAttribute(it->name()))
             continue;
-        if (!attribute.namespaceURI().isNull())
+        if (!it->namespaceURI().isNull())
             return;
         // FIXME: Background URL may depend on the base URL and can't be shared. Disallow caching.
-        if (attribute.name() == backgroundAttr)
+        if (it->name() == backgroundAttr)
             return;
-        result.attributesAndValues.append(std::make_pair(attribute.localName().impl(), attribute.value()));
+        result.attributesAndValues.append(std::make_pair(it->localName().impl(), it->value()));
     }
     if (result.attributesAndValues.isEmpty())
         return;
     // Attribute order doesn't matter. Sort for easy equality comparison.
     std::sort(result.attributesAndValues.begin(), result.attributesAndValues.end(), attributeNameSort);
     // The cache key is non-null when the tagName is set.
     result.tagName = element.localName().impl();
 }
 
 static unsigned computePresentationAttributeCacheHash(const PresentationAttributeCacheKey& key)
@@ skipping 24 matching lines @@
     } else {
         cacheValue = 0;
     }
 
     RefPtr<StylePropertySet> style;
     if (cacheHash && cacheValue->value) {
         style = cacheValue->value->value;
         cacheCleaner.didHitPresentationAttributeCache();
     } else {
         style = MutableStylePropertySet::create(element.isSVGElement() ? SVGAttributeMode : HTMLAttributeMode);
-        unsigned size = element.attributeCount();
-        for (unsigned i = 0; i < size; ++i) {
-            const Attribute& attribute = element.attributeItem(i);
-            element.collectStyleForPresentationAttribute(attribute.name(), attribute.value(), toMutableStylePropertySet(style));
-        }
+        AttributeIteratorAccessor attributes = element.attributesIterator();
+        AttributeConstIterator end = attributes.end();
+        for (AttributeConstIterator it = attributes.begin(); it != end; ++it)
+            element.collectStyleForPresentationAttribute(it->name(), it->value(), toMutableStylePropertySet(style));
     }
 
     if (!cacheHash || cacheValue->value)
         return style.release();
 
     OwnPtr<PresentationAttributeCacheEntry> newEntry = adoptPtr(new PresentationAttributeCacheEntry);
     newEntry->key = cacheKey;
     newEntry->value = style;
 
     static const unsigned presentationAttributeCacheMaximumSize = 4096;
     if (presentationAttributeCache().size() > presentationAttributeCacheMaximumSize) {
         // FIXME: Discarding the entire cache when it gets too big is probably bad
         // since it creates a perf "cliff". Perhaps we should use an LRU?
         presentationAttributeCache().clear();
         presentationAttributeCache().set(cacheHash, newEntry.release());
     } else {
         cacheValue->value = newEntry.release();
     }
 
     return style.release();
 }
 
 } // namespace WebCore