According to http://dev.w3.org/2006/webapi/FileAPI/#dfn-encoding , if a Blob can not be parsed as the given or calculated encoding, bytes that can not be read must be substituted with U+FFFD. This test creates a Blob with illegal UTF-8 bytes and then attempts to read it as UTF-8 text, and checks that the proper character substitution occurs.
WebKit passes this test.
Created attachment 110249 [details]
Comment on attachment 110249 [details]
Clearing flags on attachment: 110249
Committed r97543: <http://trac.webkit.org/changeset/97543>
All reviewed patches have been landed. Closing bug.