Credential Manager: Pass the correct credential type to the embedder.

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 WebURL& avatarURL, const WebURL& federation)
     : WebCredential(PlatformFederatedCredential::create(id, name, avatarURL, federation))
 {
 }
 
 void WebFederatedCredential::assign(const WebFederatedCredential& other)
 {
     m_platformCredential = other.m_platformCredential;
 }
 
 WebURL WebFederatedCredential::federation() const
 {
     return static_cast<PlatformFederatedCredential*>(m_platformCredential.get())->federation();
 }
 
+WebFederatedCredential::WebFederatedCredential(PlatformCredential* credential)
+    : WebCredential(credential)
+{
+}
+
+WebFederatedCredential& WebFederatedCredential::operator=(PlatformCredential* credential)
+{
+    m_platformCredential = credential;
+    return *this;
+}
+
 } // namespace blink