The HTML parser synchronously creates custom elements

third_party/WebKit/Source/core/dom/Document.cpp

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index 8c1c043632fe2f3c0c3b70dba4d5747165f0aaf8..7fd71c2799b43df89f11f6c18eb1d1bfb9c6dbee 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -107,6 +107,7 @@
 #include "core/dom/VisitedLinkState.h"
 #include "core/dom/XMLDocument.h"
 #include "core/dom/custom/CustomElement.h"
+#include "core/dom/custom/CustomElementsRegistry.h"
 #include "core/dom/custom/V0CustomElementMicrotaskRunQueue.h"
 #include "core/dom/custom/V0CustomElementRegistrationContext.h"
 #include "core/dom/shadow/ElementShadow.h"
@@ -461,6 +462,12 @@ Document::Document(const DocumentInit& initializer, DocumentClassFlags documentC
 
         m_fetcher = m_frame->loader().documentLoader()->fetcher();
         FrameFetchContext::provideDocumentToContext(m_fetcher->context(), this);
+
+        CustomElementsRegistry* registry = m_frame->localDOMWindow()
+            ? m_frame->localDOMWindow()->maybeCustomElements()
+            : nullptr;
+        if (registry && m_registrationContext)
+            registry->entangle(m_registrationContext);
     } else if (m_importsController) {
         m_fetcher = FrameFetchContext::createContextAndFetcher(nullptr, this);
     } else {