media: Make MediaKeys ref-counted.

media/base/browser_cdm.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 MEDIA_BASE_BROWSER_CDM_H_
-#define MEDIA_BASE_BROWSER_CDM_H_
-
-#include "base/memory/scoped_ptr.h"
-#include "media/base/media_export.h"
-#include "media/base/media_keys.h"
-#include "media/base/player_tracker.h"
-
-namespace media {
-
-// Interface for browser side CDMs.
-class MEDIA_EXPORT BrowserCdm : public MediaKeys, public PlayerTracker {
- public:
-  ~BrowserCdm() override;
-
-  // Virtual destructor. For most subclasses we can delete on the caller thread.
-  virtual void DeleteOnCorrectThread();
-
- protected:
-   BrowserCdm();
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(BrowserCdm);
-};
-
-struct MEDIA_EXPORT BrowserCdmDeleter {
-  inline void operator()(BrowserCdm* ptr) const {
-    ptr->DeleteOnCorrectThread();
-  }
-};
-
-using ScopedBrowserCdmPtr = scoped_ptr<BrowserCdm, BrowserCdmDeleter>;
-
-}  // namespace media
-
-#endif  // MEDIA_BASE_BROWSER_CDM_H_