Implement "Key Presence" step in "Encrypted Block Encounted" algorithm in EME.

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"
@@ skipping 34 matching lines @@
                       int init_data_length,
                       const std::string& session_id) OVERRIDE;
   virtual void CancelKeyRequest(const std::string& key_system,
                                 const std::string& session_id) OVERRIDE;
   // Decrypts |encrypted| buffer. |encrypted| should not be NULL. |encrypted|
   // will signal if an integrity check must be performed before decryption.
   // Returns a DecoderBuffer with the decrypted data if the decryption
   // succeeded through |decrypt_cb|.
   virtual void Decrypt(const scoped_refptr<DecoderBuffer>& encrypted,
                        const DecryptCB& decrypt_cb) OVERRIDE;
+  virtual void Stop() OVERRIDE;
 
  private:
   // Helper class that manages the decryption key and HMAC key. The HMAC key
   // may be NULL.
   class DecryptionKey {
    public:
     explicit DecryptionKey(const std::string& secret);
     ~DecryptionKey();
 
     // Creates the encryption key, and derives the WebM decryption key and HMAC.
@@ skipping 47 matching lines @@
   static uint32 next_session_id_;
 
   DecryptorClient* const client_;
 
   DISALLOW_COPY_AND_ASSIGN(AesDecryptor);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_CRYPTO_AES_DECRYPTOR_H_