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

Source/core/css/StyleSheetList.cpp

Index: Source/core/css/StyleSheetList.cpp
diff --git a/Source/core/css/StyleSheetList.cpp b/Source/core/css/StyleSheetList.cpp
index 17ad7b4013c41cffdf8be12ff2c24f537fa21b8d..10f5905ba4e8c1901c991d69e8419a337541515c 100644
--- a/Source/core/css/StyleSheetList.cpp
+++ b/Source/core/css/StyleSheetList.cpp
@@ -64,7 +64,7 @@ StyleSheet* StyleSheetList::item(unsigned index)
     return index < sheets.size() ? sheets[index].get() : 0;
 }
 
-HTMLStyleElement* StyleSheetList::getNamedItem(const String& name) const
+HTMLStyleElement* StyleSheetList::getNamedItem(const AtomicString& name) const
 {
     if (!m_treeScope)
         return 0;