introduce DocumentParserClient to receive parser stopped notification

Source/core/dom/DocumentParserClient.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 DocumentParserClient_h
+#define DocumentParserClient_h
+
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class DocumentParserClient : public WillBeGarbageCollectedMixin {
+public:
+    // This callback is called when all data pushed to parser has been consumed.
+    virtual void notifyParserStopped() = 0;
+
+protected:
+    DocumentParserClient() { }
+};
+
+} // namespace blink
+
+#endif // DocumentParserClient_h