createElement should not transmit exceptions but report them.

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 60 matching lines @@
 
 static CustomElementDefinition* definitionForName(const Document& document,
                                                   const QualifiedName& name) {
   if (CustomElementRegistry* registry = CustomElement::registry(document))
     return registry->definitionForName(name.localName());
   return nullptr;
 }
 
 HTMLElement* CustomElement::createCustomElementSync(
     Document& document,
-    const AtomicString& localName,
-    ExceptionState& exceptionState) {
+    const AtomicString& localName) {
   return createCustomElementSync(
       document,
-      QualifiedName(nullAtom, localName, HTMLNames::xhtmlNamespaceURI),
-      exceptionState);
-}
-
-HTMLElement* CustomElement::createCustomElementSync(
-    Document& document,
-    const QualifiedName& tagName,
-    ExceptionState& exceptionState) {
-  DCHECK(shouldCreateCustomElement(tagName));
-
-  // To create an element:
-  // https://dom.spec.whatwg.org/#concept-create-element
-  // 6. If definition is non-null, then:
-  // 6.1. If the synchronous custom elements flag is set:
-  if (CustomElementDefinition* definition =
-          definitionForName(document, tagName))
-    return definition->createElementSync(document, tagName, exceptionState);
-
-  return createUndefinedElement(document, tagName);
+      QualifiedName(nullAtom, localName, HTMLNames::xhtmlNamespaceURI));
 }
 
 HTMLElement* CustomElement::createCustomElementSync(
     Document& document,
     const QualifiedName& tagName) {
   DCHECK(shouldCreateCustomElement(tagName));
-
-  // 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 (CustomElementDefinition* definition =
           definitionForName(document, tagName))
     return definition->createElementSync(document, tagName);
-
   return createUndefinedElement(document, tagName);
 }
 
 HTMLElement* CustomElement::createCustomElementAsync(
     Document& document,
     const QualifiedName& tagName) {
   DCHECK(shouldCreateCustomElement(tagName));
 
   // To create an element:
   // https://dom.spec.whatwg.org/#concept-create-element
@@ skipping 106 matching lines @@
   if (!registry)
     return;
   if (CustomElementDefinition* definition =
           registry->definitionForName(element->localName()))
     definition->enqueueUpgradeReaction(element);
   else
     registry->addCandidate(element);
 }
 
 }  // namespace blink