Credential Manager: Add platform-exposed Credential objects.

Source/platform/exported/WebFederatedCredential.cpp

+// 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.
+
+#include "config.h"
+#include "public/platform/WebFederatedCredential.h"
+
+#include "platform/credentialmanager/PlatformFederatedCredential.h"
+
+namespace blink {
+
+WebFederatedCredential::WebFederatedCredential(const WebString& id, const WebString& name, const WebString& avatarURL, const WebString& federation)
+    : WebCredential(PlatformFederatedCredential::create(id, name, avatarURL, federation))
+{
+}
+
+void WebFederatedCredential::assign(const WebFederatedCredential& other)
+{
+    m_private = other.m_private;
+}
+
+WebString WebFederatedCredential::federation() const
+{
+    return static_cast<PlatformFederatedCredential*>(m_private.get())->federation();
+}
+
+} // namespace blink
+