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

Source/core/html/shadow/SpinButtonElement.h

Index: Source/core/html/shadow/SpinButtonElement.h
diff --git a/Source/core/html/shadow/SpinButtonElement.h b/Source/core/html/shadow/SpinButtonElement.h
index 715f4343adf909067a285f62c4f6bab198727da5..a7490366545adb8a78d17a549d05b33001f078b4 100644
--- a/Source/core/html/shadow/SpinButtonElement.h
+++ b/Source/core/html/shadow/SpinButtonElement.h
@@ -97,6 +97,20 @@ inline SpinButtonElement* toSpinButtonElement(Element* element)
     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