Preserve data if possible when dropping Items from entities. Partial solution for BUKKIT-15

src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java

@@ -288,8 +288,16 @@ public class CraftEventFactory {
         victim.expToDrop = event.getDroppedExp();
 
         for (org.bukkit.inventory.ItemStack stack : event.getDrops()) {
+            if (stack == null || stack.getType() == Material.AIR) continue;
+
+            if (stack instanceof CraftItemStack) {
+                // Use the internal item to preserve possible data.
+                victim.a(((CraftItemStack) stack).getHandle(), 0.0f);
+            }
+            else {
                 world.dropItemNaturally(entity.getLocation(), stack);
             }
+        }
 
         return event;
     }
@@ -310,8 +318,14 @@ public class CraftEventFactory {
         for (org.bukkit.inventory.ItemStack stack : event.getDrops()) {
             if (stack == null || stack.getType() == Material.AIR) continue;
 
+            if (stack instanceof CraftItemStack) {
+                // Use the internal item to preserve possible data.
+                victim.a(((CraftItemStack) stack).getHandle(), 0.0f);
+            }
+            else {
                 world.dropItemNaturally(entity.getLocation(), stack);
             }
+        }
 
         return event;
     }