Make calls to AtomicString(const String&) explicit in dom/

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 f9cd4eec6d78473b65a590e135e358bb7f7c5228..14c082d5ec7fbcdbee0a3e6d0239f861338086ef 100644
--- a/Source/core/dom/DatasetDOMStringMap.cpp
+++ b/Source/core/dom/DatasetDOMStringMap.cpp
@@ -107,7 +107,9 @@ static bool isValidPropertyName(const String& name)
     return true;
 }
 
-static String convertPropertyNameToAttributeName(const String& name)
+// This returns an AtomicString because attribute names are always stored
+// as AtomicString types in Element (see setAttribute()).
+static AtomicString convertPropertyNameToAttributeName(const String& name)
 {
     StringBuilder builder;
     builder.append("data-");
@@ -122,7 +124,7 @@ static String convertPropertyNameToAttributeName(const String& name)
             builder.append(character);
     }
 
-    return builder.toString();
+    return builder.toAtomicString();
 }
 
 void DatasetDOMStringMap::ref()
@@ -185,13 +187,13 @@ void DatasetDOMStringMap::setItem(const String& name, const String& value, Excep
         return;
     }
 
-    m_element->setAttribute(convertPropertyNameToAttributeName(name), value, exceptionState);
+    m_element->setAttribute(convertPropertyNameToAttributeName(name), AtomicString(value), exceptionState);
 }
 
 bool DatasetDOMStringMap::deleteItem(const String& name)
 {
     if (isValidPropertyName(name)) {
-        String attributeName = convertPropertyNameToAttributeName(name);
+        AtomicString attributeName = convertPropertyNameToAttributeName(name);
         if (m_element->hasAttribute(attributeName)) {
             m_element->removeAttribute(attributeName);
             return true;