Credential Manager: Align 'FederatedCredential' with the spec.

Source/modules/credentialmanager/PasswordCredentialData.idl

Index: Source/modules/credentialmanager/PasswordCredentialData.idl
diff --git a/Source/modules/credentialmanager/PasswordCredentialData.idl b/Source/modules/credentialmanager/PasswordCredentialData.idl
new file mode 100644
index 0000000000000000000000000000000000000000..8739fe66f868bfb06cd889bab32262c274f3362a
--- /dev/null
+++ b/Source/modules/credentialmanager/PasswordCredentialData.idl
@@ -0,0 +1,9 @@
+// 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-passwordcredentialdata
+
+dictionary PasswordCredentialData : LocallyStoredCredentialData {
+    DOMString password;
+};