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

media/filters/decrypting_demuxer_stream.h

Index: media/filters/decrypting_demuxer_stream.h
diff --git a/media/filters/decrypting_demuxer_stream.h b/media/filters/decrypting_demuxer_stream.h
index c65df176fa003432d12d4db8932dc8a7fa9cc37e..b98727751f36c6704e178942fb6bf3c3b4bfde73 100644
--- a/media/filters/decrypting_demuxer_stream.h
+++ b/media/filters/decrypting_demuxer_stream.h
@@ -67,8 +67,10 @@ class MEDIA_EXPORT DecryptingDemuxerStream : public DemuxerStream {
     kWaitingForKey
   };
 
-  // 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);
 
   // Callback for DemuxerStream::Read().
   void DecryptBuffer(DemuxerStream::Status status,