Fix compilation errors

transport/src/main/java/io/netty/channel/socket/oio/AbstractOioMessageChannel.java

@@ -10,15 +10,13 @@ import java.util.Queue;
 
 abstract class AbstractOioMessageChannel extends AbstractOioChannel {
 
-    private final ChannelBufferHolder<Object> firstOut = ChannelBufferHolders.messageBuffer();
-
     protected AbstractOioMessageChannel(Channel parent, Integer id) {
         super(parent, id);
     }
 
     @Override
-    protected ChannelBufferHolder<Object> firstOut() {
-        return firstOut;
+    protected ChannelBufferHolder<?> newOutboundBuffer() {
+        return ChannelBufferHolders.messageBuffer();
     }
 
     @Override

transport/src/main/java/io/netty/channel/socket/oio/AbstractOioStreamChannel.java

@@ -10,16 +10,13 @@ import java.io.IOException;
 
 abstract class AbstractOioStreamChannel extends AbstractOioChannel {
 
-    private final ChannelBufferHolder<?> firstOut = ChannelBufferHolders.byteBuffer();
-
     protected AbstractOioStreamChannel(Channel parent, Integer id) {
         super(parent, id);
     }
 
     @Override
-    @SuppressWarnings("unchecked")
-    protected ChannelBufferHolder<Object> firstOut() {
-        return (ChannelBufferHolder<Object>) firstOut;
+    protected ChannelBufferHolder<?> newOutboundBuffer() {
+        return ChannelBufferHolders.byteBuffer();
     }
 
     @Override

transport/src/main/java/io/netty/channel/socket/oio/OioDatagramChannel.java

@@ -47,7 +47,6 @@ public class OioDatagramChannel extends AbstractOioMessageChannel
 
     private final MulticastSocket socket;
     private final DatagramChannelConfig config;
-    private final ChannelBufferHolder<Object> out = ChannelBufferHolders.messageBuffer();
     private final java.net.DatagramPacket tmpPacket = new java.net.DatagramPacket(EMPTY_DATA, 0);
 
     private static MulticastSocket newSocket() {
@@ -103,8 +102,8 @@ public class OioDatagramChannel extends AbstractOioMessageChannel
     }
 
     @Override
-    protected ChannelBufferHolder<Object> firstOut() {
-        return out;
+    protected ChannelBufferHolder<?> newOutboundBuffer() {
+        return ChannelBufferHolders.messageBuffer();
     }
 
     @Override

transport/src/main/java/io/netty/channel/socket/oio/OioServerSocketChannel.java

@@ -161,7 +161,7 @@ public class OioServerSocketChannel extends AbstractOioMessageChannel
     }
 
     @Override
-    protected ChannelBufferHolder<Object> firstOut() {
+    protected ChannelBufferHolder<?> newOutboundBuffer() {
         return ChannelBufferHolders.discardBuffer();
     }
 

transport/src/main/java/io/netty/channel/socket/oio/OioSocketChannel.java

@@ -42,7 +42,6 @@ public class OioSocketChannel extends AbstractOioStreamChannel
 
     private final Socket socket;
     private final SocketChannelConfig config;
-    private final ChannelBufferHolder<?> out = ChannelBufferHolders.byteBuffer();
     private InputStream is;
     private OutputStream os;
 
@@ -96,9 +95,8 @@ public class OioSocketChannel extends AbstractOioStreamChannel
     }
 
     @Override
-    @SuppressWarnings("unchecked")
-    protected ChannelBufferHolder<Object> firstOut() {
-        return (ChannelBufferHolder<Object>) out;
+    protected ChannelBufferHolder<?> newOutboundBuffer() {
+        return ChannelBufferHolders.byteBuffer();
     }
 
     @Override