Add a scoped context object for synchronous CE creation

third_party/WebKit/Source/bindings/core/v8/custom/V8HTMLElementCustom.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 "bindings/core/v8/V8HTMLElement.h"
 
 #include "bindings/core/v8/DOMWrapperWorld.h"
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/ScriptCustomElementDefinition.h"
 #include "bindings/core/v8/V8Binding.h"
@@ skipping 41 matching lines @@
         "HTMLElement",
         info.Holder(),
         isolate);
 
     Element* element;
     if (definition->constructionStack().isEmpty()) {
         // This is an element being created with 'new' from script
         // TODO(kojii): When HTMLElementFactory has an option not to queue
         // upgrade, call that instead of HTMLElement. HTMLElement is enough
         // for now, but type extension will require HTMLElementFactory.
+        Document* context = window->customElementCreationContext();
+        if (!context)
+            context = window->document();
+
         element = HTMLElement::create(
             QualifiedName(nullAtom, definition->descriptor().localName(), HTMLNames::xhtmlNamespaceURI),
-            *window->document());
+            *context);
         // TODO(davaajav): write this as one call to setCustomElementState instead of two
         element->setCustomElementState(CustomElementState::Undefined);
         element->setCustomElementDefinition(definition);
     } else {
         element = definition->constructionStack().last();
         if (element) {
             // This is an element being upgraded that has called super
             definition->constructionStack().last().clear();
         } else {
             // During upgrade an element has invoked the same constructor
@@ skipping 13 matching lines @@
         wrapperType,
         info.Holder());
     // If the element had a wrapper, we now update and return that
     // instead.
     v8SetReturnValue(info, wrapper);
 
     wrapper->SetPrototype(scriptState->context(), definition->prototype()).ToChecked();
 }
 
 } // namespace blink