OkResponseHandler should return a FullHttpResponse.

Motivation:
Currently OkResponseHandler returns a DefaultHttpResponse which is not
correct and it should be returning complete http response.

Modifications:
Updated OkResponseHandler to return an instance of
DefaultFullHttpResponse.

Result:
It is not possible to add compression to the example without getting any
errors.

example/src/main/java/io/netty/example/http/cors/OkResponseHandler.java

@@ -18,7 +18,8 @@
 import io.netty.channel.ChannelFutureListener;
 import io.netty.channel.ChannelHandlerAdapter;
 import io.netty.channel.ChannelHandlerContext;
-import io.netty.handler.codec.http.DefaultHttpResponse;
+import io.netty.handler.codec.http.DefaultFullHttpResponse;
+import io.netty.handler.codec.http.FullHttpResponse;
 import io.netty.handler.codec.http.HttpResponseStatus;
 import io.netty.handler.codec.http.HttpVersion;
 
@@ -30,7 +31,7 @@ public class OkResponseHandler extends ChannelHandlerAdapter {
 
     @Override
     public void channelRead(ChannelHandlerContext ctx, Object msg) {
-        final DefaultHttpResponse response = new DefaultHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
+        final FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK);
         response.headers().set("custom-response-header", "Some value");
         ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
     }