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

Source/platform/credentialmanager/PlatformLocalCredential.h

Index: Source/platform/credentialmanager/PlatformLocalCredential.h
diff --git a/Source/platform/credentialmanager/PlatformLocalCredential.h b/Source/platform/credentialmanager/PlatformLocalCredential.h
index 40b1a820ee0cb6e35a2aaf448992ec8ef75fb917..ce6d236491bfc0767f0ed985c2c6ac17d72a2a44 100644
--- a/Source/platform/credentialmanager/PlatformLocalCredential.h
+++ b/Source/platform/credentialmanager/PlatformLocalCredential.h
@@ -19,6 +19,8 @@ public:
 
     const String& password() const { return m_password; }
 
+    virtual bool isLocal() override { return true; }
+
 private:
     PlatformLocalCredential(const String& id, const String& name, const KURL& avatarURL, const String& password);