Set callback interface on WebCDMSession after creation.

public/platform/WebContentDecryptionModuleSession.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 44 matching lines @@
         // FIXME: Remove this method once Chromium updated to use the new parameters.
         virtual void error(MediaKeyErrorCode, unsigned long systemCode) = 0;
         virtual void error(WebContentDecryptionModuleException, unsigned long systemCode, const WebString& message) = 0;
 
     protected:
         virtual ~Client();
     };
 
     virtual ~WebContentDecryptionModuleSession();
 
+    virtual void setClientInterface(Client*) = 0;
     virtual WebString sessionId() const = 0;
 
     // FIXME: Remove these methods once the new methods are implemented in Chromium.
     virtual void initializeNewSession(const WebString& mimeType, const unsigned char* initData, size_t initDataLength) = 0;
     virtual void update(const unsigned char* response, size_t responseLength) = 0;
     virtual void release() = 0;
 
     virtual void initializeNewSession(const WebString& initDataType, const unsigned char* initData, size_t initDataLength, const WebString& sessionType, WebContentDecryptionModuleResult);
     virtual void update(const unsigned char* response, size_t responseLength, WebContentDecryptionModuleResult);
     virtual void release(WebContentDecryptionModuleResult);
 };
 
 } // namespace blink
 
 #endif // WebContentDecryptionModuleSession_h