[webcrypto] Define the DOMException OperationError.

This is defined by the Web Crypto spec:
https://dvcs.w3.org/hg/webcrypto-api/raw-file/tip/spec/Overview.html#SubtleCrypto-Exceptions

BUG=245025

Review URL: https://codereview.chromium.org/258203003

git-svn-id: svn://svn.chromium.org/blink/trunk@173416 bbb929c8-8fbe-4397-9dbb-9b2b20218538