Introduce isHTMLAnchorElement and toHTMLAnchorElement

Source/core/page/DragController.cpp

Index: Source/core/page/DragController.cpp
diff --git a/Source/core/page/DragController.cpp b/Source/core/page/DragController.cpp
index 0ad707ddee59332c7d03f874a336e0be68d8f863..0e011589a14afdd6e746df52a8433fe7355cecc0 100644
--- a/Source/core/page/DragController.cpp
+++ b/Source/core/page/DragController.cpp
@@ -643,8 +643,8 @@ Node* DragController::draggableNode(const Frame* src, Node* startNode, const Int
                     return node;
                 }
                 if ((m_dragSourceAction & DragSourceActionLink)
-                    && node->hasTagName(HTMLNames::aTag)
-                    && static_cast<HTMLAnchorElement*>(node)->isLiveLink()) {
+                    && isHTMLAnchorElement(node)
+                    && toHTMLAnchorElement(node)->isLiveLink()) {
                     state.m_dragType = static_cast<DragSourceAction>(state.m_dragType | DragSourceActionLink);
                     return node;
                 }