Allow setContentDecryptionModule() to get called when setting is done.

media/filters/decrypting_audio_decoder.h

Index: media/filters/decrypting_audio_decoder.h
diff --git a/media/filters/decrypting_audio_decoder.h b/media/filters/decrypting_audio_decoder.h
index 70cbc5632268c13130e6e6231bc6901a43b80f69..9ea211a1ab9f7bae4ab9f91d58db31912b9508f3 100644
--- a/media/filters/decrypting_audio_decoder.h
+++ b/media/filters/decrypting_audio_decoder.h
@@ -66,8 +66,10 @@ class MEDIA_EXPORT DecryptingAudioDecoder : public AudioDecoder {
     kError
   };
 
-  // Callback for DecryptorHost::RequestDecryptor().
-  void SetDecryptor(Decryptor* decryptor);
+  // Callback for DecryptorHost::RequestDecryptor(). |decryptor_attached_cb| is
+  // called when the decryptor has been completely attached to the pipeline.
+  void SetDecryptor(Decryptor* decryptor,
+                    const DecryptorAttachedCB& decryptor_attached_cb);
 
   // Initializes the audio decoder on the |decryptor_| with |config_|.
   void InitializeDecoder();