Add support for World Workers skipping ticks without being removed from the worker list.

src/main/java/net/minecraftforge/common/WorldWorkerManager.java

@@ -25,6 +25,7 @@ public class WorldWorkerManager
 {
     private static List<IWorker> workers = new ArrayList<IWorker>();
     private static long startTime = -1;
+    private static int index = 0;
 
     public static void tick(boolean start)
     {
@@ -34,6 +35,7 @@ public class WorldWorkerManager
             return;
         }
 
+        index = 0;
         IWorker task = getNext();
         if (task == null)
             return;
@@ -43,14 +45,18 @@ public class WorldWorkerManager
             time = 10; //If ticks are lagging, give us at least 10ms to do something.
         time += System.currentTimeMillis();
 
-        while (System.currentTimeMillis() < time)
+        while (System.currentTimeMillis() < time && task != null)
         {
-            task.work();
+            boolean again = task.doWork();
 
             if (!task.hasWork())
             {
-                time = 0; //Break loop
                 remove(task);
+                task = getNext();
+            }
+            else if (!again)
+            {
+                task = getNext();
             }
         }
     }
@@ -62,12 +68,13 @@ public class WorldWorkerManager
 
     private static synchronized IWorker getNext()
     {
-        return workers.size() > 0 ? workers.get(0) : null;
+        return workers.size() > index ? workers.get(index++) : null;
     }
 
     private static synchronized void remove(IWorker worker)
     {
         workers.remove(worker);
+        index--;
     }
 
     //Internal only, used to clear everything when the server shuts down.
@@ -79,6 +86,17 @@ public class WorldWorkerManager
     public static interface IWorker
     {
         boolean hasWork();
-        void work();
+
+        default void work() {}; //TODO: Remove in 1.13.
+
+        /**
+         * Perform a task, returning true from this will have the manager call this function again this tick if there is time left.
+         * Returning false will skip calling this worker until next tick.
+         */
+        default boolean doWork()
+        {
+            work();
+            return true;
+        }
     }
 }