WebCrypto API doesn't provide for a way to specify different extractability for keys in a generated key pair, so if the caller wants a non-extractable private key, the public key is not extractable too. This makes no sense, and is tracked as <https://www.w3.org/Bugs/Public/show_bug.cgi?id=23013>/<https://www.w3.org/Bugs/Public/show_bug.cgi?id=23695>.
Created attachment 219095 [details] proposed patch
Committed <http://trac.webkit.org/changeset/160496> (with a bad ChangeLog, thank you commit-log-editor).