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

Source/core/dom/DatasetDOMStringMap.cpp

Index: Source/core/dom/DatasetDOMStringMap.cpp
diff --git a/Source/core/dom/DatasetDOMStringMap.cpp b/Source/core/dom/DatasetDOMStringMap.cpp
index c6a9584ca3682579cb4898091bb795ce41a18429..a7871bfa9aec933ff769881a2ee297e362d0b869 100644
--- a/Source/core/dom/DatasetDOMStringMap.cpp
+++ b/Source/core/dom/DatasetDOMStringMap.cpp
@@ -154,9 +154,6 @@ void DatasetDOMStringMap::deref()
 
 void DatasetDOMStringMap::getNames(Vector<String>& names)
 {
-    if (!m_element->hasAttributes())
-        return;
-
     AttributeCollection attributes = m_element->attributes();
     AttributeCollection::const_iterator end = attributes.end();
     for (AttributeCollection::const_iterator it = attributes.begin(); it != end; ++it) {
@@ -167,9 +164,6 @@ void DatasetDOMStringMap::getNames(Vector<String>& names)
 
 String DatasetDOMStringMap::item(const String& name)
 {
-    if (!m_element->hasAttributes())
-        return String();
-
     AttributeCollection attributes = m_element->attributes();
     AttributeCollection::const_iterator end = attributes.end();
     for (AttributeCollection::const_iterator it = attributes.begin(); it != end; ++it) {
@@ -182,9 +176,6 @@ String DatasetDOMStringMap::item(const String& name)
 
 bool DatasetDOMStringMap::contains(const String& name)
 {
-    if (!m_element->hasAttributes())
-        return false;
-
     AttributeCollection attributes = m_element->attributes();
     AttributeCollection::const_iterator end = attributes.end();
     for (AttributeCollection::const_iterator it = attributes.begin(); it != end; ++it) {