BlobView is useful when you want to view portions of a blob without reading the entire thing into memory at a time. Since you're using the entire blob here, and don't seem to be using the utility functions defined by BlobView, I think you could use DataView just as well.  

Just wrap your ArrayBuffer with a DataView and use that.  Then create the blob from it when you're done.  (And that way, you hopefully don't need a custom version of BlobView.)