Support Document constructor.

third_party/WebKit/Source/core/dom/Document.cpp

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index ecf025f9b8bbdf102ff34cfc044e347942b63755..514a832b90614041ea0a521861f65327b14eb1f5 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -491,6 +491,14 @@ class Document::NetworkStateObserver final
   DEFINE_INLINE_VIRTUAL_TRACE() { ContextLifecycleObserver::Trace(visitor); }
 };
 
+Document* Document::Create(const Document& document) {
+  Document* new_document = new Document(
+      DocumentInit::FromContext(const_cast<Document*>(&document), BlankURL()));
+  new_document->SetSecurityOrigin(document.GetSecurityOrigin());
+  new_document->SetContextFeatures(document.GetContextFeatures());
+  return new_document;
+}
+
 Document::Document(const DocumentInit& initializer,
                    DocumentClassFlags document_classes)
     : ContainerNode(0, kCreateDocument),