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

webkit/media/crypto/ppapi_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 WEBKIT_MEDIA_CRYPTO_PPAPI_DECRYPTOR_H_
 #define WEBKIT_MEDIA_CRYPTO_PPAPI_DECRYPTOR_H_
 
 #include <string>
 
 #include "base/memory/ref_counted.h"
@@ skipping 25 matching lines @@
   virtual void AddKey(const std::string& key_system,
                       const uint8* key,
                       int key_length,
                       const uint8* init_data,
                       int init_data_length,
                       const std::string& session_id) OVERRIDE;
   virtual void CancelKeyRequest(const std::string& key_system,
                                 const std::string& session_id) OVERRIDE;
   virtual void Decrypt(const scoped_refptr<media::DecoderBuffer>& encrypted,
                        const DecryptCB& decrypt_cb) OVERRIDE;
+  virtual void Stop() OVERRIDE;
 
  private:
   // Callback for the plugin to hand back the decrypted data.
   void DataReady(const DecryptCB& decrypt_cb, const uint8* data, int data_size);
 
   // TODO(xhwang): Need to figure out how the CDM plugin fires key events
   // (e.g. KeyMessage).
   media::DecryptorClient* client_;
   scoped_refptr<webkit::ppapi::PluginInstance> cdm_plugin_;
 
   DISALLOW_COPY_AND_ASSIGN(PpapiDecryptor);
 };
 
 }  // namespace webkit_media
 
 #endif  // WEBKIT_MEDIA_CRYPTO_PPAPI_DECRYPTOR_H_