Add support for encrypted WebM files as defined in the RFC.

media/crypto/aes_decryptor.h

 // Copyright (c) 2012 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_CRYPTO_AES_DECRYPTOR_H_
 #define MEDIA_CRYPTO_AES_DECRYPTOR_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/hash_tables.h"
 #include "base/memory/ref_counted.h"
-#include "base/synchronization/lock.h"
 #include "media/base/media_export.h"
+#include "media/crypto/decryptor.h"
 
 namespace crypto {
 class SymmetricKey;
 }
 
 namespace media {
 
 class DecoderBuffer;
 
 // Decrypts AES encrypted buffer into unencrypted buffer.
-class MEDIA_EXPORT AesDecryptor {
+class MEDIA_EXPORT AesDecryptor : public Decryptor {
  public:
   AesDecryptor();
-  ~AesDecryptor();
+  virtual ~AesDecryptor();
 
+  // Decryptor implementation.
   // Add a |key_id| and |key| pair to the key system. The key is not limited to
   // a decryption key. It can be any data that the key system accepts, such as
   // a license. If multiple calls of this function set different keys for the
   // same |key_id|, the older key will be replaced by the newer key.
-  void AddKey(const uint8* key_id, int key_id_size,
-              const uint8* key, int key_size);
+  virtual void AddKey(const uint8* key_id, int key_id_size,
+                      const uint8* key, int key_size) OVERRIDE;
 
   // Decrypt |input| buffer. The |input| should not be NULL.
   // Return a DecoderBuffer with the decrypted data if decryption succeeded.
   // Return NULL if decryption failed.
-  scoped_refptr<DecoderBuffer> Decrypt(
-      const scoped_refptr<DecoderBuffer>& input);
+  virtual scoped_refptr<DecoderBuffer> Decrypt(
+      const scoped_refptr<DecoderBuffer>& input) OVERRIDE;
 
  private:
   // KeyMap owns the crypto::SymmetricKey* and must delete them when they are
   // not needed any more.
   typedef base::hash_map<std::string, crypto::SymmetricKey*> KeyMap;
   KeyMap key_map_;
-  base::Lock lock_;
 
   DISALLOW_COPY_AND_ASSIGN(AesDecryptor);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_CRYPTO_AES_DECRYPTOR_H_