Make HTMLImportTreeNode own the whole import tree.

Source/core/html/imports/HTMLImportTreeRoot.h

 // Copyright 2014 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.
 
 #ifndef HTMLImportTreeRoot_h
 #define HTMLImportTreeRoot_h
 
 #include "core/html/imports/HTMLImport.h"
 #include "platform/Timer.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace WebCore {
 
+class HTMLImportChild;
+
 class HTMLImportTreeRoot : public HTMLImport {
 public:
     static PassOwnPtr<HTMLImportTreeRoot> create(Document*);
 
+    virtual ~HTMLImportTreeRoot();
+
     // HTMLImport
     virtual Document* document() const OVERRIDE;
     virtual bool isDone() const OVERRIDE;
     virtual void stateWillChange() OVERRIDE;
     virtual void stateDidChange() OVERRIDE;
 
     void scheduleRecalcState();
 
+    HTMLImportChild* add(PassOwnPtr<HTMLImportChild>);
+    HTMLImportChild* find(const KURL&) const;
+
 private:
     explicit HTMLImportTreeRoot(Document*);
 
     void recalcTimerFired(Timer<HTMLImportTreeRoot>*);
 
     Document* m_document;
     Timer<HTMLImportTreeRoot> m_recalcTimer;
+
+    // List of import which has been loaded or being loaded.
+    typedef Vector<OwnPtr<HTMLImportChild> > ImportList;
+    ImportList m_imports;
 };
 
 DEFINE_TYPE_CASTS(HTMLImportTreeRoot, HTMLImport, import, import->isRoot(), import.isRoot());
 
 }
 
 #endif