Replace static_cast with safe casting methods

Source/bindings/v8/custom/V8CSSValueCustom.cpp

Index: Source/bindings/v8/custom/V8CSSValueCustom.cpp
diff --git a/Source/bindings/v8/custom/V8CSSValueCustom.cpp b/Source/bindings/v8/custom/V8CSSValueCustom.cpp
index 0c862c4f8de7c3847bbdfc2849a15ceb9d701369..dfbff496df03666b599f14e2f5bbaa8c1078a24d 100644
--- a/Source/bindings/v8/custom/V8CSSValueCustom.cpp
+++ b/Source/bindings/v8/custom/V8CSSValueCustom.cpp
@@ -52,9 +52,9 @@ v8::Handle<v8::Object> wrap(CSSValue* impl, v8::Handle<v8::Object> creationConte
     if (impl->isCSSFilterValue())
         return wrap(static_cast<CSSFilterValue*>(impl), creationContext, isolate);
     if (impl->isValueList())
-        return wrap(static_cast<CSSValueList*>(impl), creationContext, isolate);
+        return wrap(toCSSValueList(impl), creationContext, isolate);
     if (impl->isPrimitiveValue())
-        return wrap(static_cast<CSSPrimitiveValue*>(impl), creationContext, isolate);
+        return wrap(toCSSPrimitiveValue(impl), creationContext, isolate);
     if (impl->isSVGPaint())
         return wrap(static_cast<SVGPaint*>(impl), creationContext, isolate);
     if (impl->isSVGColor())