Introduce and use type casting functions for several HTMLCollection types

Source/bindings/v8/custom/V8HTMLCollectionCustom.cpp

Index: Source/bindings/v8/custom/V8HTMLCollectionCustom.cpp
diff --git a/Source/bindings/v8/custom/V8HTMLCollectionCustom.cpp b/Source/bindings/v8/custom/V8HTMLCollectionCustom.cpp
index b67355a1ddff41f112f685e3eef9b794cc246f8c..05883e60ceefbb521beb33f07ceb2f2a57b31ee3 100644
--- a/Source/bindings/v8/custom/V8HTMLCollectionCustom.cpp
+++ b/Source/bindings/v8/custom/V8HTMLCollectionCustom.cpp
@@ -45,11 +45,11 @@ v8::Handle<v8::Object> wrap(HTMLCollection* impl, v8::Handle<v8::Object> creatio
     ASSERT(impl);
     switch (impl->type()) {
     case FormControls:
-        return wrap(static_cast<HTMLFormControlsCollection*>(impl), creationContext, isolate);
+        return wrap(toHTMLFormControlsCollection(impl), creationContext, isolate);
     case SelectOptions:
-        return wrap(static_cast<HTMLOptionsCollection*>(impl), creationContext, isolate);
+        return wrap(toHTMLOptionsCollection(impl), creationContext, isolate);
     case DocAll:
-        return wrap(static_cast<HTMLAllCollection*>(impl), creationContext, isolate);
+        return wrap(toHTMLAllCollection(impl), creationContext, isolate);
     default:
         break;
     }