Add support for Blob constructor in blobworkers test since BlobBuilder is deprecated and has been removed from firefox

whitespace change

fix cleanup for blobworker; ensure worker termination, ensure url revocation, and ensure addTest is only called once.

style fixes.

factor out cleanup & fail functions
Merge pull request #1141 from cagerton/blob-constructor

Add support for Blob constructor in blobworkers test since BlobBuilder i...