createElement should not transmit exceptions but report them.

third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.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 CustomElementDefinition_h
 #define CustomElementDefinition_h
 
 #include "bindings/core/v8/ScriptValue.h"
 #include "core/CoreExport.h"
 #include "core/dom/custom/CustomElementDescriptor.h"
@@ skipping 31 matching lines @@
   // |CustomElementConstructor| to |ScriptValue|. Replace
   // |getConstructorForScript()| by |getConstructor() ->
   // CustomElementConstructor|.
   virtual ScriptValue getConstructorForScript() = 0;
 
   using ConstructionStack = HeapVector<Member<Element>, 1>;
   ConstructionStack& constructionStack() { return m_constructionStack; }
 
   HTMLElement* createElementForConstructor(Document&);
   virtual HTMLElement* createElementSync(Document&, const QualifiedName&) = 0;
-  virtual HTMLElement* createElementSync(Document&,
-                                         const QualifiedName&,
-                                         ExceptionState&) = 0;
   HTMLElement* createElementAsync(Document&, const QualifiedName&);
 
   void upgrade(Element*);
 
   virtual bool hasConnectedCallback() const = 0;
   virtual bool hasDisconnectedCallback() const = 0;
   virtual bool hasAdoptedCallback() const = 0;
   bool hasAttributeChangedCallback(const QualifiedName&) const;
   bool hasStyleAttributeChangedCallback() const;
 
@@ skipping 43 matching lines @@
   ConstructionStack m_constructionStack;
   HashSet<AtomicString> m_observedAttributes;
   bool m_hasStyleAttributeChangedCallback;
 
   void enqueueAttributeChangedCallbackForAllAttributes(Element*);
 };
 
 }  // namespace blink
 
 #endif  // CustomElementDefinition_h