Implement "create an element" when sync for Custom Element V1

third_party/WebKit/Source/core/dom/custom/CustomElement.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/dom/custom/CustomElement.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/QualifiedName.h"
 #include "core/dom/custom/CEReactionsScope.h"
 #include "core/dom/custom/CustomElementDefinition.h"
@@ skipping 82 matching lines @@
     // To create an element:
     // https://dom.spec.whatwg.org/#concept-create-element
     // 6. If definition is non-null, then:
     HTMLElement* element;
     if (CustomElementsRegistry* registry = CustomElement::registry(document)) {
         if (CustomElementDefinition* definition = registry->definitionForName(tagName.localName())) {
             // 6.2. If the synchronous custom elements flag is not set:
             if (flags & AsynchronousCustomElements)
                 return createCustomElementAsync(document, *definition, tagName);
 
-            // TODO(kojii): Synchronous mode implementation coming after async.
+            // When invoked from "create an element for a token":
+            // https://html.spec.whatwg.org/multipage/syntax.html#create-an-element-for-the-token
+            // 7. If this step throws an exception, then report the exception,
+            // and let element be instead a new element that implements
+            // HTMLUnknownElement.
+            if (flags & CreatedByParser)
+                return definition->createCustomElementIgnoringErrors(document, tagName);
+
+            // 6.1. If the synchronous custom elements flag is set:
+            return definition->createCustomElement(document, tagName);
         }
     }
 
     if (V0CustomElement::isValidName(tagName.localName()) && document.registrationContext()) {
         Element* v0element = document.registrationContext()->createCustomTagElement(document, tagName);
         SECURITY_DCHECK(v0element->isHTMLElement());
         element = toHTMLElement(v0element);
     } else {
         element = HTMLElement::create(tagName, document);
     }
@@ skipping 24 matching lines @@
 void CustomElement::enqueueUpgradeReaction(Element* element, CustomElementDefinition* definition)
 {
     // CEReactionsScope must be created by [CEReactions] in IDL,
     // or callers must setup explicitly if it does not go through bindings.
     DCHECK(CEReactionsScope::current());
     CEReactionsScope::current()->enqueue(element,
         new CustomElementUpgradeReaction(definition));
 }
 
 } // namespace blink