Remove AtomicStringImpl.

Source/core/dom/CheckedRadioButtons.cpp

Index: Source/core/dom/CheckedRadioButtons.cpp
diff --git a/Source/core/dom/CheckedRadioButtons.cpp b/Source/core/dom/CheckedRadioButtons.cpp
index a628b439cfd2b6e88bb3c0062a6339583c40e243..d8d7a46d11324b619780933d27a877b4e6c5770a 100644
--- a/Source/core/dom/CheckedRadioButtons.cpp
+++ b/Source/core/dom/CheckedRadioButtons.cpp
@@ -260,7 +260,7 @@ void CheckedRadioButtons::removeButton(HTMLInputElement* element)
     if (it->value->isEmpty()) {
         // FIXME: We may skip deallocating the empty RadioButtonGroup for
         // performance improvement. If we do so, we need to change the key type
-        // of m_nameToGroupMap from AtomicStringImpl* to RefPtr<AtomicStringImpl>.
+        // of m_nameToGroupMap from StringImpl* to AtomicString.
         m_nameToGroupMap->remove(it);
         if (m_nameToGroupMap->isEmpty())
             m_nameToGroupMap.clear();