Cleanup <static_cast>: Switch to toFoo for Accessibility Objects.

Source/core/accessibility/AccessibilityListBoxOption.h

Index: Source/core/accessibility/AccessibilityListBoxOption.h
diff --git a/Source/core/accessibility/AccessibilityListBoxOption.h b/Source/core/accessibility/AccessibilityListBoxOption.h
index 987b5bc7754e8fa5279bce11abb6c1e6f1762a6e..364273dc830d6091318ba06c361103a99b21dc58 100644
--- a/Source/core/accessibility/AccessibilityListBoxOption.h
+++ b/Source/core/accessibility/AccessibilityListBoxOption.h
@@ -66,6 +66,7 @@ public:
 private:
     HTMLElement* m_optionElement;
 
+    virtual bool isListBoxOption() const OVERRIDE { return true; }
     virtual bool canHaveChildren() const OVERRIDE { return false; }
     virtual bool computeAccessibilityIsIgnored() const OVERRIDE;
 
@@ -74,6 +75,21 @@ private:
     AccessibilityObject* listBoxOptionAccessibilityObject(HTMLElement*) const;
 };
 
+inline AccessibilityListBoxOption* toAccessibilityListBoxOption(AccessibilityObject* object)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isListBoxOption());
+    return static_cast<AccessibilityListBoxOption*>(object);
+}
+
+inline const AccessibilityListBoxOption* toAccessibilityListBoxOption(const AccessibilityObject* object)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isListBoxOption());
+    return static_cast<const AccessibilityListBoxOption*>(object);
+}
+
+// This will catch anyone doing an unnecessary cast.
+void toAccessibilityListBoxOption(const AccessibilityListBoxOption*);
+
 } // namespace WebCore
 
 #endif // AccessibilityListBoxOption_h