Credential Management: Rename 'notifySignedOut' to 'requireUserMediation'. (1/3)

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.
 
 [
     RuntimeEnabled=CredentialManager,
     GarbageCollected
 ] interface CredentialsContainer {
     [CallWith=ScriptState] Promise request(optional Dictionary options);
     [CallWith=ScriptState, TypeChecking=Interface] Promise notifySignedIn(Credential credential);
     [CallWith=ScriptState, TypeChecking=Interface] Promise notifyFailedSignIn(Credential credential);
-    [CallWith=ScriptState] Promise notifySignedOut();
+    [CallWith=ScriptState] Promise requireUserMediation();
 };