Let ContentSecurityPolicy shared between imports and the master.

Source/core/html/imports/HTMLImportChild.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 38 matching lines @@
 // An import tree node subclas to encapsulate imported document
 // lifecycle. This class is owned by LinkStyle. The actual loading
 // is done by HTMLImportLoader, which can be shared among multiple
 // HTMLImportChild of same link URL.
 //
 // HTMLImportChild implements ResourceClient through ResourceOwner
 // so that it can speculatively request linked resources while it is unblocked.
 //
 class HTMLImportChild FINAL : public HTMLImport, public HTMLImportLoaderClient, public ResourceOwner<RawResource> {
 public:
-    HTMLImportChild(const KURL&, bool createdByParser);
+    HTMLImportChild(Document&, const KURL&, bool createdByParser);
     virtual ~HTMLImportChild();
 
     HTMLLinkElement* link() const;
     Document* importedDocument() const;
     const KURL& url() const { return m_url; }
 
     void wasAlreadyLoaded();
     void startLoading(const ResourcePtr<RawResource>&);
     void importDestroyed();
 
@@ skipping 25 matching lines @@
     virtual void notifyFinished(Resource*) OVERRIDE { }
 
     // HTMLImportLoaderClient
     virtual void didFinishLoading() OVERRIDE;
 
     void didFinish();
     void createLoader();
     void shareLoader(HTMLImportChild*);
     void ensureLoader();
 
+    Document& m_master;
     KURL m_url;
     CustomElementMicrotaskImportStep* m_customElementMicrotaskStep;
     RefPtr<HTMLImportLoader> m_loader;
     HTMLImportChildClient* m_client;
 };
 
 inline HTMLImportChild* toHTMLImportChild(HTMLImport* import)
 {
     ASSERT(!import || import->isChild());
     return static_cast<HTMLImportChild*>(import);
 }
 
 } // namespace WebCore
 
 #endif // HTMLImportChild_h