createElement should not transmit exceptions but report them.

third_party/WebKit/Source/bindings/core/v8/ScriptCustomElementDefinition.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 ScriptCustomElementDefinition_h
 #define ScriptCustomElementDefinition_h
 
 #include "bindings/core/v8/ScopedPersistent.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "core/CoreExport.h"
@@ skipping 28 matching lines @@
       const v8::Local<v8::Function>& adoptedCallback,
       const v8::Local<v8::Function>& attributeChangedCallback,
       const HashSet<AtomicString>& observedAttributes);
 
   virtual ~ScriptCustomElementDefinition() = default;
 
   v8::Local<v8::Object> constructor() const;
   v8::Local<v8::Object> prototype() const;
 
   HTMLElement* createElementSync(Document&, const QualifiedName&) override;
-  HTMLElement* createElementSync(Document&,
-                                 const QualifiedName&,
-                                 ExceptionState&) override;
 
   bool hasConnectedCallback() const override;
   bool hasDisconnectedCallback() const override;
   bool hasAdoptedCallback() const override;
 
   void runConnectedCallback(Element*) override;
   void runDisconnectedCallback(Element*) override;
   void runAdoptedCallback(Element*,
                           Document* oldOwner,
                           Document* newOwner) override;
@@ skipping 17 matching lines @@
   // Implementations of |CustomElementDefinition|
   ScriptValue getConstructorForScript() final;
   bool runConstructor(Element*) override;
   Element* runConstructor();
 
   void runCallback(v8::Local<v8::Function>,
                    Element*,
                    int argc = 0,
                    v8::Local<v8::Value> argv[] = nullptr);
 
+  HTMLElement* handleCreateElementSyncException(Document&,
+                                                const QualifiedName& tagName,
+                                                v8::Isolate*,
+                                                ExceptionState&);
+
   RefPtr<ScriptState> m_scriptState;
   ScopedPersistent<v8::Object> m_constructor;
   ScopedPersistent<v8::Object> m_prototype;
   ScopedPersistent<v8::Function> m_connectedCallback;
   ScopedPersistent<v8::Function> m_disconnectedCallback;
   ScopedPersistent<v8::Function> m_adoptedCallback;
   ScopedPersistent<v8::Function> m_attributeChangedCallback;
 };
 
 }  // namespace blink
 
 #endif  // ScriptCustomElementDefinition_h