Introduce and use type casting functions for several HTMLCollection types

Source/core/dom/TagCollection.h

Index: Source/core/dom/TagCollection.h
diff --git a/Source/core/dom/TagCollection.h b/Source/core/dom/TagCollection.h
index 9314a1d1146a3779957493a1db74e64777656926..6b97db7f2a765918f046cb4b8143d9856f1f0c71 100644
--- a/Source/core/dom/TagCollection.h
+++ b/Source/core/dom/TagCollection.h
@@ -56,6 +56,8 @@ protected:
     AtomicString m_localName;
 };
 
+DEFINE_TYPE_CASTS(TagCollection, LiveNodeListBase, collection, collection->type() == TagCollectionType, collection.type() == TagCollectionType);
+
 class HTMLTagCollection FINAL : public TagCollection {
 public:
     static PassRefPtrWillBeRawPtr<HTMLTagCollection> create(ContainerNode& rootNode, CollectionType type, const AtomicString& localName)
@@ -72,6 +74,8 @@ private:
     AtomicString m_loweredLocalName;
 };
 
+DEFINE_TYPE_CASTS(HTMLTagCollection, LiveNodeListBase, collection, collection->type() == HTMLTagCollectionType, collection.type() == HTMLTagCollectionType);
+
 inline bool HTMLTagCollection::elementMatches(const Element& testElement) const
 {
     // Implements http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-getelementsbytagname