[w3c/webauthn] b8c602: Fix #624 - Change PublicKeyCredential.clientExtens...

  Branch: refs/heads/master
  Home:   https://github.com/w3c/webauthn
  Commit: b8c60278ad53479d03a2247e1360c33869f58e92
      https://github.com/w3c/webauthn/commit/b8c60278ad53479d03a2247e1360c33869f58e92
  Author: J.C. Jones <jc@mozilla.com>
  Date:   2017-10-18 (Wed, 18 Oct 2017)

  Changed paths:
    M index.bs

  Log Message:
  -----------
  Fix #624 - Change PublicKeyCredential.clientExtensionResults to an operation

The attribute `clientExtensionResults` is a typedef of `record<DOMString, any>`.
The WebIDL spec says "Records must not be used as the type of an attribute
or constant", so this is not legal.

This commit changes the attribute `clientExtensionResults` into an operation
`getClientExtensionResults()`.