Bug 1419643 - Don't need to lookup custom element definition for a non-custom element

Tag UXP Issue #1344

1 files changed, 8 insertions, 5 deletions

diff --git a/dom/html/nsHTMLContentSink.cpp b/dom/html/nsHTMLContentSink.cpp
index 7d60fffb5..920ded728 100644
--- a/dom/html/nsHTMLContentSink.cpp
+++ b/dom/html/nsHTMLContentSink.cpp
@@ -275,12 +275,18 @@ NS_NewHTMLElement(Element** aResult, already_AddRefed<mozilla::dom::NodeInfo>&&
 
   int32_t tag = parserService->HTMLCaseSensitiveAtomTagToId(name);
 
+  bool isCustomElementName = (tag == eHTMLTag_userdefined &&
+                              nsContentUtils::IsCustomElementName(name));
+  bool isCustomElement = isCustomElementName || aIs;
+  MOZ_ASSERT_IF(aDefinition, isCustomElement);
+
   // https://dom.spec.whatwg.org/#concept-create-element
   // We only handle the "synchronous custom elements flag is set" now.
   // For the unset case (e.g. cloning a node), see bug 1319342 for that.
   // Step 4.
   CustomElementDefinition* definition = aDefinition;
-  if (!definition && CustomElementRegistry::IsCustomElementEnabled()) {
+  if (CustomElementRegistry::IsCustomElementEnabled() && isCustomElement &&
+      !definition) {
     definition =
       nsContentUtils::LookupCustomElementDefinition(nodeInfo->GetDocument(),
                                                     nodeInfo->LocalName(),
@@ -363,8 +369,6 @@ NS_NewHTMLElement(Element** aResult, already_AddRefed<mozilla::dom::NodeInfo>&&
 
   // Per the Custom Element specification, unknown tags that are valid custom
   // element names should be HTMLElement instead of HTMLUnknownElement.
-  bool isCustomElementName = (tag == eHTMLTag_userdefined &&
-                              nsContentUtils::IsCustomElementName(name));
   if (isCustomElementName) {
     NS_IF_ADDREF(*aResult = NS_NewHTMLElement(nodeInfo.forget(), aFromParser));
   } else {
@@ -375,8 +379,7 @@ NS_NewHTMLElement(Element** aResult, already_AddRefed<mozilla::dom::NodeInfo>&&
     return NS_ERROR_OUT_OF_MEMORY;
   }
 
-  if (CustomElementRegistry::IsCustomElementEnabled() &&
-      (isCustomElementName || aIs)) {
+  if (CustomElementRegistry::IsCustomElementEnabled() && isCustomElement) {
     (*aResult)->SetCustomElementData(new CustomElementData(typeAtom));
   }