Introduce toHTMLMapElement

Source/core/dom/TreeScope.cpp

Index: Source/core/dom/TreeScope.cpp
diff --git a/Source/core/dom/TreeScope.cpp b/Source/core/dom/TreeScope.cpp
index 9cd02cbcf3d4ec0c4b439280162f94870e3f7e10..68ee74a922318aa9cc34f7d6e485f8865fc58dac 100644
--- a/Source/core/dom/TreeScope.cpp
+++ b/Source/core/dom/TreeScope.cpp
@@ -205,8 +205,8 @@ HTMLMapElement* TreeScope::getImageMap(const String& url) const
     size_t hashPos = url.find('#');
     String name = (hashPos == notFound ? url : url.substring(hashPos + 1)).impl();
     if (rootNode()->document()->isHTMLDocument())
-        return static_cast<HTMLMapElement*>(m_imageMapsByName->getElementByLowercasedMapName(AtomicString(name.lower()).impl(), this));
-    return static_cast<HTMLMapElement*>(m_imageMapsByName->getElementByMapName(AtomicString(name).impl(), this));
+        return toHTMLMapElement(m_imageMapsByName->getElementByLowercasedMapName(AtomicString(name.lower()).impl(), this));
+    return toHTMLMapElement(m_imageMapsByName->getElementByMapName(AtomicString(name).impl(), this));
 }
 
 Node* nodeFromPoint(Document* document, int x, int y, LayoutPoint* localPoint)