Move HTMLTagCollection to its own file

Source/core/dom/TagCollection.cpp

Index: Source/core/dom/TagCollection.cpp
diff --git a/Source/core/dom/TagCollection.cpp b/Source/core/dom/TagCollection.cpp
index 0e2bb71ff2ded1708087dc4d19134fadab64594d..2025c649387a4e5be6c9ff739a1acf9c97e1335a 100644
--- a/Source/core/dom/TagCollection.cpp
+++ b/Source/core/dom/TagCollection.cpp
@@ -56,10 +56,4 @@ bool TagCollection::elementMatches(const Element& testNode) const
     return m_namespaceURI == starAtom || m_namespaceURI == testNode.namespaceURI();
 }
 
-HTMLTagCollection::HTMLTagCollection(ContainerNode& rootNode, const AtomicString& localName)
-    : TagCollection(rootNode, HTMLTagCollectionType, starAtom, localName)
-    , m_loweredLocalName(localName.lower())
-{
-}
-
 } // namespace WebCore