2 files changed, 24 insertions, 0 deletions
diff --git a/dom/base/CustomElementRegistry.cpp b/dom/base/CustomElementRegistry.cpp
index 43e4e7e2a..6cd213210 100644
--- a/dom/base/CustomElementRegistry.cpp
+++ b/dom/base/CustomElementRegistry.cpp
@@ -273,6 +273,23 @@ CustomElementRegistry::LookupCustomElementDefinition(const nsAString& aLocalName
   return nullptr;
 }
 
+CustomElementDefinition*
+CustomElementRegistry::LookupCustomElementDefinition(JSContext* aCx,
+                                                     JSObject* aConstructor) const
+{
+  JS::Rooted<JSObject*> constructor(aCx, js::CheckedUnwrap(aConstructor));
+
+  const auto& ptr = mConstructors.lookup(constructor);
+  if (!ptr) {
+    return nullptr;
+  }
+
+  CustomElementDefinition* definition = mCustomDefinitions.Get(ptr->value());
+  MOZ_ASSERT(definition, "Definition must be found in mCustomDefinitions");
+
+  return definition;
+}
+
 void
 CustomElementRegistry::RegisterUnresolvedElement(Element* aElement, nsIAtom* aTypeName)
 {
diff --git a/dom/base/CustomElementRegistry.h b/dom/base/CustomElementRegistry.h
index 9034dd7ea..8ef0785af 100644
--- a/dom/base/CustomElementRegistry.h
+++ b/dom/base/CustomElementRegistry.h
@@ -128,6 +128,10 @@ struct CustomElementDefinition
 
   // The document custom element order.
   uint32_t mDocOrder;
+
+  bool IsCustomBuiltIn() {
+    return mType != mLocalName;
+  }
 };
 
 class CustomElementRegistry final : public nsISupports,
@@ -155,6 +159,9 @@ public:
   CustomElementDefinition* LookupCustomElementDefinition(
     const nsAString& aLocalName, const nsAString* aIs = nullptr) const;
 
+  CustomElementDefinition* LookupCustomElementDefinition(
+    JSContext* aCx, JSObject *aConstructor) const;
+
   /**
    * Enqueue created callback or register upgrade candidate for
    * newly created custom elements, possibly extending an existing type.