Refactoring: Extract DocumentInit for capture Document construction parameter.

Source/core/html/HTMLImportsController.cpp

Index: Source/core/html/HTMLImportsController.cpp
diff --git a/Source/core/html/HTMLImportsController.cpp b/Source/core/html/HTMLImportsController.cpp
index 203d95536da0ff00c754489f3caca4e6e12e8ad4..4e91e2526b47f6e321bb8712a21742561db5ce4f 100644
--- a/Source/core/html/HTMLImportsController.cpp
+++ b/Source/core/html/HTMLImportsController.cpp
@@ -179,8 +179,7 @@ HTMLImportLoader::State HTMLImportLoader::startParsing(const ResourceResponse& r
     if (!controller()->cachedResourceLoader()->canAccess(m_resource.get()))
         return StateError;
 
-    m_importedDocument = HTMLDocument::create(0, response.url());
-    m_importedDocument->setImport(this);
+    m_importedDocument = HTMLDocument::create(DocumentInitializer(response.url(), 0, this));
     m_writer = DocumentWriter::create(m_importedDocument.get(), response.mimeType(), response.textEncodingName());
 
     return StateLoading;