[eme] Handle multiple calls to MediaKeySession.close()

media/base/content_decryption_module.h

 // Copyright 2013 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_CONTENT_DECRYPTION_MODULE_H_
 #define MEDIA_BASE_CONTENT_DECRYPTION_MODULE_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 107 matching lines @@
 
   // Updates a session specified by |session_id| with |response|.
   virtual void UpdateSession(const std::string& session_id,
                              const std::vector<uint8_t>& response,
                              std::unique_ptr<SimpleCdmPromise> promise) = 0;
 
   // Closes the session specified by |session_id|. The CDM should resolve or
   // reject the |promise| when the call has been processed. This may be before
   // the session is closed. Once the session is closed, a SessionClosedCB must
   // also be called.
+  // Note that the EME spec executes the close() action asynchronously, so
+  // CloseSession() may be called multiple times on the same session.
   virtual void CloseSession(const std::string& session_id,
                             std::unique_ptr<SimpleCdmPromise> promise) = 0;
 
   // Removes stored session data associated with the session specified by
   // |session_id|.
   virtual void RemoveSession(const std::string& session_id,
                              std::unique_ptr<SimpleCdmPromise> promise) = 0;
 
   // Returns the CdmContext associated with |this|. The returned CdmContext is
   // owned by |this| and the caller needs to make sure it is not used after
@@ skipping 50 matching lines @@
 
 // Called when the CDM changes the expiration time of a session.
 // See http://w3c.github.io/encrypted-media/#update-expiration
 typedef base::Callback<void(const std::string& session_id,
                             base::Time new_expiry_time)>
     SessionExpirationUpdateCB;
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_CONTENT_DECRYPTION_MODULE_H_