Introduce DEFINE_INLINE_BOX_TYPE_CASTS, and use it

Source/core/rendering/InlineFlowBox.h

Index: Source/core/rendering/InlineFlowBox.h
diff --git a/Source/core/rendering/InlineFlowBox.h b/Source/core/rendering/InlineFlowBox.h
index 3ada554086019a982a50f835809d0aa87d74aa8a..066098fdac87d9e6129ee51eec83fcaa7a8dd4bb 100644
--- a/Source/core/rendering/InlineFlowBox.h
+++ b/Source/core/rendering/InlineFlowBox.h
@@ -350,20 +350,7 @@ private:
 #endif
 };
 
-inline InlineFlowBox* toInlineFlowBox(InlineBox* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isInlineFlowBox());
-    return static_cast<InlineFlowBox*>(object);
-}
-
-inline const InlineFlowBox* toInlineFlowBox(const InlineBox* object)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isInlineFlowBox());
-    return static_cast<const InlineFlowBox*>(object);
-}
-
-// This will catch anyone doing an unnecessary cast.
-void toInlineFlowBox(const InlineFlowBox*);
+DEFINE_INLINE_BOX_TYPE_CASTS(InlineFlowBox);
 
 #ifdef NDEBUG
 inline void InlineFlowBox::checkConsistency() const