Follow vanilla settings behavior. Fixes BUKKIT-5069

A vanilla server does a series of checks for the client black-listing
certain chat types (commands or chat). This change changes a CB
whitelist to the vanilla blacklist behavior.

src/main/java/net/minecraft/server/PlayerConnection.java

@@ -758,7 +758,7 @@ public class PlayerConnection implements PacketPlayInListener {
     }
 
     public void a(PacketPlayInChat packetplayinchat) {
-        if (this.player.getChatFlags() == EnumChatVisibility.HIDDEN) {
+        if (this.player.dead || this.player.getChatFlags() == EnumChatVisibility.HIDDEN) { // CraftBukkit - dead men tell no tales
             ChatMessage chatmessage = new ChatMessage("chat.cannotSend", new Object[0]);
 
             chatmessage.b().setColor(EnumChatFormat.RED);
@@ -835,14 +835,13 @@ public class PlayerConnection implements PacketPlayInListener {
 
     // CraftBukkit start
     public void chat(String s, boolean async) {
-        if (s.isEmpty()) {
+        if (s.isEmpty() || this.player.getChatFlags() == EnumChatVisibility.HIDDEN) {
             return;
         }
 
-        if (!this.player.dead) {
         if (s.startsWith("/")) {
             this.handleCommand(s);
-            } else if (this.player.getChatFlags() != EnumChatVisibility.FULL) {
+        } else if (this.player.getChatFlags() == EnumChatVisibility.SYSTEM) {
             // Do nothing, this is coming from a plugin
         } else {
             Player player = this.getPlayer();
@@ -906,7 +905,6 @@ public class PlayerConnection implements PacketPlayInListener {
             }
         }
     }
-    }
     // CraftBukkit end
 
     private void handleCommand(String s) {