Implemented PlayerShearEntityEvent in EntityMushroomCow.

Due to the Vanilla client overzealously predicting things, shearing produces
client-side artifacts. See BUKKIT-611 for more information.

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

@@ -0,0 +1,49 @@
+package net.minecraft.server;
+
+public class EntityMushroomCow extends EntityCow {
+
+    public EntityMushroomCow(World world) {
+        super(world);
+        this.texture = "/mob/redcow.png";
+        this.b(0.9F, 1.3F);
+    }
+
+    public boolean b(EntityHuman entityhuman) {
+        ItemStack itemstack = entityhuman.inventory.getItemInHand();
+
+        if (itemstack != null && itemstack.id == Item.BOWL.id && this.getAge() >= 0) {
+            entityhuman.inventory.setItem(entityhuman.inventory.itemInHandIndex, new ItemStack(Item.MUSHROOM_SOUP));
+            return true;
+        } else if (itemstack != null && itemstack.id == Item.SHEARS.id && this.getAge() >= 0) {
+            // CraftBukkit start
+            org.bukkit.event.player.PlayerShearEntityEvent event = new org.bukkit.event.player.PlayerShearEntityEvent((org.bukkit.entity.Player) entityhuman.getBukkitEntity(), this.getBukkitEntity());
+            this.world.getServer().getPluginManager().callEvent(event);
+
+            if (event.isCancelled()) {
+                return false;
+            }
+            // CraftBukkit end
+
+            this.die();
+            EntityCow entitycow = new EntityCow(this.world);
+
+            entitycow.setPositionRotation(this.locX, this.locY, this.locZ, this.yaw, this.pitch);
+            entitycow.setHealth(this.getHealth());
+            entitycow.V = this.V;
+            this.world.addEntity(entitycow);
+            this.world.a("largeexplode", this.locX, this.locY + (double) (this.length / 2.0F), this.locZ, 0.0D, 0.0D, 0.0D);
+
+            for (int i = 0; i < 5; ++i) {
+                this.world.addEntity(new EntityItem(this.world, this.locX, this.locY + (double) this.length, this.locZ, new ItemStack(Block.RED_MUSHROOM)));
+            }
+
+            return true;
+        } else {
+            return super.b(entityhuman);
+        }
+    }
+
+    protected EntityAnimal createChild(EntityAnimal entityanimal) {
+        return new EntityMushroomCow(this.world);
+    }
+}