Allow writing with void promise if IdleStateHandler is configured in pipeline.

Motivation:

Allow writing with void promise if IdleStateHandler is configured in the pipeline for read timeout events.

Modifications:

Better performance.

Result:

No more ChannelFutureListeners are created if IdleStateHandler is only configured for read timeouts allowing for writing to the channel with void promise.

handler/src/main/java/io/netty/handler/timeout/IdleStateHandler.java

@@ -256,13 +256,16 @@ public class IdleStateHandler extends ChannelDuplexHandler {
 
     @Override
     public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
-        promise.addListener(new ChannelFutureListener() {
+        // Allow writing with void promise if handler is only configured for read timeout events.
-            @Override
+        if (writerIdleTimeNanos > 0 || allIdleTimeNanos > 0) {
-            public void operationComplete(ChannelFuture future) throws Exception {
+            promise.addListener(new ChannelFutureListener() {
-                lastWriteTime = System.nanoTime();
+                @Override
-                firstWriterIdleEvent = firstAllIdleEvent = true;
+                public void operationComplete(ChannelFuture future) throws Exception {
-            }
+                    lastWriteTime = System.nanoTime();
-        });
+                    firstWriterIdleEvent = firstAllIdleEvent = true;
+                }
+            });
+        }
         ctx.write(msg, promise);
     }