Share Custom Element registration contexts between related documents.

Source/core/loader/DocumentLoader.cpp

Index: Source/core/loader/DocumentLoader.cpp
diff --git a/Source/core/loader/DocumentLoader.cpp b/Source/core/loader/DocumentLoader.cpp
index bd0d5d123dfd32f1adcf9a6a74dbdd61a43c48e6..ef3c8588147cf2a7b548bebfea22a9d36f72e309 100644
--- a/Source/core/loader/DocumentLoader.cpp
+++ b/Source/core/loader/DocumentLoader.cpp
@@ -30,6 +30,7 @@
 #include "config.h"
 #include "core/loader/DocumentLoader.h"
 
+#include "core/dom/CustomElementRegistrationContextualizer.h"
 #include "core/dom/DOMImplementation.h"
 #include "core/dom/Document.h"
 #include "core/dom/DocumentParser.h"
@@ -1055,6 +1056,7 @@ PassRefPtr<DocumentWriter> DocumentLoader::createWriterFor(Frame* frame, const D
     // Create a new document before clearing the frame, because it may need to
     // inherit an aliased security context.
     RefPtr<Document> document = DOMImplementation::createDocument(mimeType, frame, url, frame->inViewSourceMode());
+    CustomElementRegistrationContextualizer::didCreateDocument(CustomElementRegistrationContextualizer::Loader, document.get());
     if (document->isPluginDocument() && document->isSandboxed(SandboxPlugins))
         document = SinkDocument::create(frame, url);
     bool shouldReuseDefaultView = frame->loader()->stateMachine()->isDisplayingInitialEmptyDocument() && frame->document()->isSecureTransitionTo(url);