createElement should not transmit exceptions but report them.

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

 // 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.
 
 #ifndef CustomElement_h
 #define CustomElement_h
 
 #include "core/CoreExport.h"
 #include "core/HTMLNames.h"
 #include "core/dom/Element.h"
@@ skipping 48 matching lines @@
       }
     }
 
     return !isHyphenatedSpecElementName(name);
   }
 
   static bool shouldCreateCustomElement(const AtomicString& localName);
   static bool shouldCreateCustomElement(const QualifiedName&);
 
   static HTMLElement* createCustomElementSync(Document&,
-                                              const AtomicString& localName,
-                                              ExceptionState&);
-  static HTMLElement* createCustomElementSync(Document&,
-                                              const QualifiedName&,
-                                              ExceptionState&);
+                                              const AtomicString& localName);
   static HTMLElement* createCustomElementSync(Document&, const QualifiedName&);
   static HTMLElement* createCustomElementAsync(Document&, const QualifiedName&);
 
   static HTMLElement* createFailedElement(Document&, const QualifiedName&);
 
   static void enqueue(Element*, CustomElementReaction*);
   static void enqueueConnectedCallback(Element*);
   static void enqueueDisconnectedCallback(Element*);
   static void enqueueAdoptedCallback(Element*,
                                      Document* oldOwner,
@@ skipping 10 matching lines @@
   // like font-face in SVG. The custom elements spec explicitly
   // disallows these as custom element names.
   // https://html.spec.whatwg.org/#valid-custom-element-name
   static bool isHyphenatedSpecElementName(const AtomicString&);
   static HTMLElement* createUndefinedElement(Document&, const QualifiedName&);
 };
 
 }  // namespace blink
 
 #endif  // CustomElement_h