Extract tree root responsibility out of HTMLImportsController.

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 HTMLImportTreeRoot : public HTMLImport {
+public:
+    static PassOwnPtr<HTMLImportTreeRoot> create(Document*);
+
+    // HTMLImport
+    virtual Document* document() const OVERRIDE;
+    virtual bool isDone() const OVERRIDE;
+    virtual void stateWillChange() OVERRIDE;
+    virtual void stateDidChange() OVERRIDE;
+
+    void scheduleRecalcState();
+
+private:
+    explicit HTMLImportTreeRoot(Document*);
+
+    void recalcTimerFired(Timer<HTMLImportTreeRoot>*);
+
+    Document* m_document;
+    Timer<HTMLImportTreeRoot> m_recalcTimer;
+};
+
+DEFINE_TYPE_CASTS(HTMLImportTreeRoot, HTMLImport, import, import->isRoot(), import.isRoot());
+
+}
+
+#endif