Deprecate CredentialRequestOptions.unmediated in favor mediation enum

third_party/WebKit/Source/modules/credentialmanager/CredentialRequestOptions.idl

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// https://w3c.github.io/webappsec/specs/credentialmanagement/#dictdef-credentialrequestoptions
+// https://w3c.github.io/webappsec-credential-management/#dictdef-credentialrequestoptions
+
+enum CredentialMediationRequirement {
+  "silent",
+  "optional",
+  "required"
+};
 
 dictionary CredentialRequestOptions {
     FederatedCredentialRequestOptions federated;
 
     boolean password = false;
-    boolean unmediated = false;
+    [DeprecateAs=CredentialManagerCredentialRequestOptionsUnmediated] boolean unmediated = false;
+    CredentialMediationRequirement mediation = "optional";
 };