Introduce LiteralSet

Source/core/dom/QualifiedName.cpp

Index: Source/core/dom/QualifiedName.cpp
diff --git a/Source/core/dom/QualifiedName.cpp b/Source/core/dom/QualifiedName.cpp
index d0228de7b2956400c4e289fdcc934becf2f10b57..71c665da67c0877be013014c5aad06ccf4e85d22 100644
--- a/Source/core/dom/QualifiedName.cpp
+++ b/Source/core/dom/QualifiedName.cpp
@@ -174,4 +174,14 @@ void createQualifiedName(void* targetAddress, StringImpl* name)
     new (reinterpret_cast<void*>(targetAddress)) QualifiedName(nullAtom, AtomicString(name), nullAtom);
 }
 
+bool lessThanByImplAddress(const QualifiedName* const& a, const QualifiedName* const& b)
+{
+    return a->impl() < b->impl();
+}
+
+bool lessThanByLocalNameImplAddress(const QualifiedName* const& a, const QualifiedName* const& b)
+{
+    return a->localName().impl() < b->localName().impl();
+}
+
 }