Introduce CdmContext interface.

media/base/cdm_context.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_CDM_CONTEXT_H_
+#define MEDIA_BASE_CDM_CONTEXT_H_
+
+#include "base/macros.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+class Decryptor;
+
+// An interface representing the context that a media pipeline needs from a
+// content decryption module (CDM) to decrypt (and decode) encrypted buffers.
+class MEDIA_EXPORT CdmContext {
+ public:
+#if defined(ENABLE_BROWSER_CDMS)
+  static const int kInvalidCdmId = 0;
+#endif
+
+  virtual ~CdmContext();
+
+  // Gets the Decryptor object associated with the CDM. Returns NULL if no
+  // Decryptor object is associated. The returned object is only guaranteed
+  // to be valid during the CDM's lifetime.
+  virtual Decryptor* GetDecryptor() = 0;
+
+#if defined(ENABLE_BROWSER_CDMS)
+  // Returns the CDM ID associated with |this|. May be kInvalidCdmId if no CDM
+  // ID is associated.
+  virtual int GetCdmId() const = 0;
+#endif
+
+ protected:
+  CdmContext();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(CdmContext);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_CDM_CONTEXT_H_