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

Source/core/platform/Scrollbar.h

Index: Source/core/platform/Scrollbar.h
diff --git a/Source/core/platform/Scrollbar.h b/Source/core/platform/Scrollbar.h
index f8de1fa6a2dc5680c5d9c8eba3f1bc3bac7bbb7e..ab44f3051f2f3bb6a44f9b1f3c3a9ad7a1b80287 100644
--- a/Source/core/platform/Scrollbar.h
+++ b/Source/core/platform/Scrollbar.h
@@ -192,6 +192,21 @@ private:
     float scrollableAreaCurrentPos() const;
 };
 
+inline Scrollbar* toScrollbar(Widget* widget)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!widget || widget->isScrollbar());
+    return static_cast<Scrollbar*>(widget);
+}
+
+inline const Scrollbar* toScrollbar(const Widget* widget)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!widget || widget->isScrollbar());
+    return static_cast<const Scrollbar*>(widget);
+}
+
+// This will catch anyone doing an unnecessary cast.
+void toScrollbar(const Scrollbar*);
+
 } // namespace WebCore
 
 #endif // Scrollbar_h