Implement CredentialsContainer::create

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

 // Copyright 2014 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-credential-management/#credentialscontainer
 
 [Exposed=Window, SecureContext]
 interface CredentialsContainer {
     [CallWith=ScriptState, MeasureAs=CredentialManagerGet] Promise get(optional CredentialRequestOptions options);
     [CallWith=ScriptState, MeasureAs=CredentialManagerStore] Promise store(Credential credential);
+    [CallWith=ScriptState, RaisesException, MeasureAs=CredentialManagerCreate] Promise create(optional CredentialCreationOptions options);
     [CallWith=ScriptState, MeasureAs=CredentialManagerRequireUserMediation] Promise requireUserMediation();
 };