Ignore JSON serializers which do not need to be serializable

Change-Id: Iccfe06495bc69d46c9c69e987776a39f824caf2f

server/tests/src/com/vaadin/tests/server/TestClassesSerializable.java

@@ -50,6 +50,8 @@ public class TestClassesSerializable extends TestCase {
             "com\\.vaadin\\.server\\.communication\\.FileUploadHandler\\$SimpleMultiPartInputStream", //
             "com\\.vaadin\\.server\\.communication\\.PushRequestHandler.*",
             "com\\.vaadin\\.server\\.communication\\.PushHandler.*", // PushHandler
+            "com\\.vaadin\\.server\\.communication\\.DateSerializer", //
+            "com\\.vaadin\\.server\\.communication\\.JSONSerializer", //
             // and its inner classes do not need to be serializable
             "com\\.vaadin\\.util\\.SerializerHelper", // fully static
             // class level filtering, also affecting nested classes and