java: Make TProtocolFactory extend Serializable.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@928901 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/java/src/org/apache/thrift/protocol/TProtocolFactory.java b/lib/java/src/org/apache/thrift/protocol/TProtocolFactory.java
index afa502b..b72e87b 100644
--- a/lib/java/src/org/apache/thrift/protocol/TProtocolFactory.java
+++ b/lib/java/src/org/apache/thrift/protocol/TProtocolFactory.java
@@ -19,12 +19,13 @@
 
 package org.apache.thrift.protocol;
 
+import java.io.Serializable;
+
 import org.apache.thrift.transport.TTransport;
 
 /**
  * Factory interface for constructing protocol instances.
- *
  */
-public interface TProtocolFactory {
+public interface TProtocolFactory extends Serializable {
   public TProtocol getProtocol(TTransport trans);
 }