CraftBukkit

--- a/net/minecraft/server/BlockLeaves.java

+++ b/net/minecraft/server/BlockLeaves.java

 import java.util.Random;

+import org.bukkit.event.block.LeavesDecayEvent; // CraftBukkit

+

 public abstract class BlockLeaves extends Block {

     public static final BlockStateBoolean DECAYABLE = BlockStateBoolean.of("decayable");

     }

     private void b(World world, BlockPosition blockposition) {

+        // CraftBukkit start

+        LeavesDecayEvent event = new LeavesDecayEvent(world.getWorld().getBlockAt(blockposition.getX(), blockposition.getY(), blockposition.getZ()));

+        world.getServer().getPluginManager().callEvent(event);

+

+        if (event.isCancelled() || world.getType(blockposition).getBlock() != this) {

+            return;

+        }