Cleanup: Start using toFoo methods as part of newly adopted coding guideline.

Source/core/html/shadow/SpinButtonElement.h

 /*
  * Copyright (C) 2006, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 79 matching lines @@
     UpDownState m_pressStartingState;
     Timer<SpinButtonElement> m_repeatingTimer;
 };
 
 inline SpinButtonElement* toSpinButtonElement(Element* element)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!element || element->isSpinButtonElement());
     return static_cast<SpinButtonElement*>(element);
 }
 
+inline SpinButtonElement* toSpinButtonElement(Node* node)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!node || toElement(node)->isSpinButtonElement());
+    return static_cast<SpinButtonElement*>(node);
+}
+
+inline const SpinButtonElement* toSpinButtonElement(const Node* node)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!node || toElement(node)->isSpinButtonElement());
+    return static_cast<const SpinButtonElement*>(node);
+}
+
+void toSpinButtonElement(const SpinButtonElement*);
+
 } // namespace
 
 #endif