Use the new callback tracker and delete the old one

webkit/plugins/ppapi/host_resource_tracker.h

-// Copyright (c) 2011 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 WEBKIT_PLUGINS_PPAPI_HOST_RESOURCE_TRACKER_H_
-#define WEBKIT_PLUGINS_PPAPI_HOST_RESOURCE_TRACKER_H_
-
-#include "base/basictypes.h"
-#include "base/compiler_specific.h"
-#include "ppapi/shared_impl/resource_tracker.h"
-
-namespace webkit {
-namespace ppapi {
-
-class HostResourceTracker : public ::ppapi::ResourceTracker {
- public:
-  HostResourceTracker();
-  virtual ~HostResourceTracker();
-
-  // ppapi::ResourceTracker overrides.
-  virtual void LastPluginRefWasDeleted(::ppapi::Resource* object) OVERRIDE;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(HostResourceTracker);
-};
-
-}  // namespace ppapi
-}  // namespace webkit
-
-#endif  // WEBKIT_PLUGINS_PPAPI_HOST_RESOURCE_TRACKER_H_