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

Source/platform/exported/WebFederatedCredential.cpp

Index: Source/platform/exported/WebFederatedCredential.cpp
diff --git a/Source/platform/exported/WebFederatedCredential.cpp b/Source/platform/exported/WebFederatedCredential.cpp
index def979b9755d684362a816c4002c3e57ad3da425..496bc530eb6ad0066d17ed6e04d255ece1bc9207 100644
--- a/Source/platform/exported/WebFederatedCredential.cpp
+++ b/Source/platform/exported/WebFederatedCredential.cpp
@@ -24,5 +24,16 @@ 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