As per https://fetch.spec.whatwg.org/#basic-fetch, if blob is null (not found e.g.), a network error should be generated. Currently we generate a 404 error response.
Created attachment 287393 [details] Patch
Created attachment 287401 [details] Fixing FileReaderLoader error generation
Comment on attachment 287401 [details] Fixing FileReaderLoader error generation Clearing flags on attachment: 287401 Committed r205190: <http://trac.webkit.org/changeset/205190>
All reviewed patches have been landed. Closing bug.