Replace ctx.channel().writeAndFlush with ctx.writeAndFlush in WebSock…

…ets handlers (netty#12540)

Motivation:

There is no actual need to call `ctx.channel().writeAndFlush` instead of `ctx.writeAndFlush`.  Using the context is also more correct as it start at the right place in the pipeline.

Modification:

Use the context and not the channel

Result:

More correct code

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketProtocolHandler.java

@@ -69,7 +69,7 @@ abstract class WebSocketProtocolHandler extends MessageToMessageDecoder<WebSocke
     protected void decode(ChannelHandlerContext ctx, WebSocketFrame frame, List<Object> out) throws Exception {
         if (frame instanceof PingWebSocketFrame) {
             frame.content().retain();
-            ctx.channel().writeAndFlush(new PongWebSocketFrame(frame.content()));
+            ctx.writeAndFlush(new PongWebSocketFrame(frame.content()));
             readIfNeeded(ctx);
             return;
         }

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerProtocolHandshakeHandler.java

@@ -142,7 +142,7 @@ private boolean checkNextUri(String uri, String websocketPath) {
     }
 
     private static void sendHttpResponse(ChannelHandlerContext ctx, HttpRequest req, HttpResponse res) {
-        ChannelFuture f = ctx.channel().writeAndFlush(res);
+        ChannelFuture f = ctx.writeAndFlush(res);
         if (!isKeepAlive(req) || res.status().code() != 200) {
             f.addListener(ChannelFutureListener.CLOSE);
         }