Keep reference to CDM to avoid it's premature destruction

media/blink/webcontentdecryptionmodule_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_WEBCONTENTDECRYPTIONMODULE_IMPL_H_
 #define MEDIA_BLINK_WEBCONTENTDECRYPTIONMODULE_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 35 matching lines @@
 
   // blink::WebContentDecryptionModule implementation.
   blink::WebContentDecryptionModuleSession* createSession() override;
 
   void setServerCertificate(
       const uint8_t* server_certificate,
       size_t server_certificate_length,
       blink::WebContentDecryptionModuleResult result) override;
 
   // Returns the CdmContext associated with this CDM, which must not be nullptr.
-  // TODO(jrummell): Figure out lifetimes, as WMPI may still use the decryptor
-  // after WebContentDecryptionModule is freed. http://crbug.com/330324
+  // Caller should keep a reference using GetCdmAdapterReference() to keep the
+  // CDM alive if necessary.
   CdmContext* GetCdmContext();
 
+  // Returns a reference to this CDM adapter.
+  CdmSessionAdapter* GetCdmAdapterReference();

[xhwang, 2016/10/07 05:02:14]

This returns a raw pointer, not a reference... Ah, CdmSessionAdapter is
refcounted. But usually for refcounted object, we put it in a scoped_refptr
immediately after it's created, and then we pretty much should never use the raw
pointer anywhere.

Actually, instead of letting WMPI hold a ref of the CdmSessionAdapter, can we
just let WIMPI hold a ref of the |cdm_|? That'll be consistent with AVDA and
MojoRendererService. Please see the comment here:

https://cs.chromium.org/chromium/src/media/base/media_keys.h?rcl=0&l=45

[jrummell, 2016/10/07 20:15:30]

Done.

+
  private:
   friend CdmSessionAdapter;
 
   // Takes reference to |adapter|.
   WebContentDecryptionModuleImpl(scoped_refptr<CdmSessionAdapter> adapter);
 
   scoped_refptr<CdmSessionAdapter> adapter_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentDecryptionModuleImpl);
 };
 
 // Allow typecasting from blink type as this is the only implementation.
 inline WebContentDecryptionModuleImpl* ToWebContentDecryptionModuleImpl(
     blink::WebContentDecryptionModule* cdm) {
   return static_cast<WebContentDecryptionModuleImpl*>(cdm);
 }
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_WEBCONTENTDECRYPTIONMODULE_IMPL_H_