Make Element::attributes() less error-prone and simplify call sites

Source/core/css/SelectorChecker.h

Index: Source/core/css/SelectorChecker.h
diff --git a/Source/core/css/SelectorChecker.h b/Source/core/css/SelectorChecker.h
index 2ca27e237fadeb59ee3aa3c90a72a2c303693832..c93b941e75926b9bc5bd1167331af029dd3758b1 100644
--- a/Source/core/css/SelectorChecker.h
+++ b/Source/core/css/SelectorChecker.h
@@ -165,9 +165,7 @@ inline bool SelectorChecker::tagMatches(const Element& element, const QualifiedN
 
 inline bool SelectorChecker::checkExactAttribute(const Element& element, const QualifiedName& selectorAttributeName, const StringImpl* value)
 {
-    if (!element.hasAttributesWithoutUpdate())
-        return false;
-    AttributeCollection attributes = element.attributes();
+    AttributeCollection attributes = element.attributesWithoutUpdate();
     AttributeCollection::const_iterator end = attributes.end();
     for (AttributeCollection::const_iterator it = attributes.begin(); it != end; ++it) {
         if (it->matches(selectorAttributeName) && (!value || it->value().impl() == value))