Replace further questionable HashMap::add usages in bindings

Source/bindings/core/v8/DOMWrapperMap.h

Index: Source/bindings/core/v8/DOMWrapperMap.h
diff --git a/Source/bindings/core/v8/DOMWrapperMap.h b/Source/bindings/core/v8/DOMWrapperMap.h
index 00c37089574d9e365f44ce0044a9137b79460e4b..75a962e2b0b2e13abed4cc0016044a5a7c26bd73 100644
--- a/Source/bindings/core/v8/DOMWrapperMap.h
+++ b/Source/bindings/core/v8/DOMWrapperMap.h
@@ -108,7 +108,7 @@ private:
             Impl* impl, KeyType* key, v8::PersistentContainerValue value)
         {
             v8::PersistentContainerValue oldValue = Get(impl, key);
-            impl->add(key, value);
+            impl->set(key, value);
             return oldValue;
         }
         static v8::PersistentContainerValue Get(const Impl* impl, KeyType* key)