EME: Make sure sessions are closed before they are destroyed

media/blink/webcontentdecryptionmodulesession_impl.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_BLINK_WEBCONTENTDECRYPTIONMODULESESSION_IMPL_H_
 #define MEDIA_BLINK_WEBCONTENTDECRYPTIONMODULESESSION_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 60 matching lines @@
   Client* client_;
 
   // Session ID is the app visible ID for this session generated by the CDM.
   // This value is not set until the CDM resolves the initializeNewSession()
   // promise.
   std::string session_id_;
 
   // Don't pass more than 1 close() event to blink::
   // TODO(jrummell): Remove this once blink tests handle close() promise and
   // closed() event.
   bool is_closed_;

[xhwang, 2016/11/11 18:52:46]

It seems possible that is_closed_ is true but has_close_been_called_ is false,
e.g. when the CDM closed the session due to resource lost etc:

The CDM may close a session at any point, such as when the session is no longer
needed or when system resources are lost.

https://w3c.github.io/encrypted-media/#session-closed

We should document it clearly here since it's a bit tricky.

[jrummell, 2016/11/11 21:14:23]

Done.

 
+  // Keep track of whether close() has been called on this session.
+  bool has_close_been_called_;
+
   base::ThreadChecker thread_checker_;
   // Since promises will live until they are fired, use a weak reference when
   // creating a promise in case this class disappears before the promise
   // actually fires.
   base::WeakPtrFactory<WebContentDecryptionModuleSessionImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentDecryptionModuleSessionImpl);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_WEBCONTENTDECRYPTIONMODULESESSION_IMPL_H_