Bug 1489437 - HTML parser should invoke custom element's callbacks before appending child nodes to it; r=smaug

Per step 3.3 of https://html.spec.whatwg.org/multipage/parsing.html#insert-a-foreign-element

Differential Revision: https://phabricator.services.mozilla.com/D5269

--HG--
extra : moz-landing-system : lando

parser/html/nsHtml5TreeOperation.cpp

@@ -178,6 +178,8 @@ nsHtml5TreeOperation::Append(nsIContent* aNode,
   MOZ_ASSERT(aBuilder->IsInDocUpdate());
   nsresult rv = NS_OK;
   nsHtml5OtherDocUpdate update(aParent->OwnerDoc(), aBuilder->GetDocument());
+  dom::AutoCEReaction autoCEReaction(
+    aParent->OwnerDoc()->GetDocGroup()->CustomElementReactionsStack(), nullptr);
   rv = aParent->AppendChildTo(aNode, false);
   if (NS_SUCCEEDED(rv)) {
     aNode->SetParserHasNotified();

testing/web-platform/meta/custom-elements/parser/parser-sets-attributes-and-children.html.ini

@@ -1,4 +0,0 @@
-[parser-sets-attributes-and-children.html]
-  [HTML parser should call connectedCallback before appending child nodes.]
-    expected: FAIL
-