Revert "Run callbacks from object's metaclass"

This reverts commit e0846c8.

activesupport/CHANGELOG

@@ -1,7 +1,5 @@
 *2.1.1 (next release)*
 
-* Run callbacks from object's metaclass [Josh Peek]
-
 * TimeWithZone: when crossing DST boundary, treat Durations of days, months or years as variable-length, and all other values as absolute length. A time + 24.hours will advance exactly 24 hours, but a time + 1.day will advance 23-25 hours, depending on the day. Ensure consistent behavior across all advancing methods [Geoff Buesing]
 
 * Fix TimeWithZone unmarshaling: coerce unmarshaled Time instances to utc, because Ruby's marshaling of Time instances doesn't respect the zone [Geoff Buesing]

activesupport/lib/active_support/callbacks.rb

@@ -269,15 +269,7 @@ def self.#{callback}_callback_chain
     #   pass
     #   stop
     def run_callbacks(kind, options = {}, &block)
-      callback_chain_method = "#{kind}_callback_chain"
-
-      # Meta class inherits Class so we don't have to merge it in 1.9
-      if RUBY_VERSION >= '1.9'
-        metaclass.send(callback_chain_method).run(self, options, &block)
-      else
-        callbacks = self.class.send(callback_chain_method) | metaclass.send(callback_chain_method)
-        callbacks.run(self, options, &block)
-      end
+      self.class.send("#{kind}_callback_chain").run(self, options, &block)
     end
   end
 end

activesupport/test/callbacks_test.rb

@@ -84,30 +84,6 @@ def test_save_person
   end
 end
 
-class MetaclassCallbacksTest < Test::Unit::TestCase
-  module ModuleWithCallbacks
-    def self.extended(object)
-      object.metaclass.before_save :raise_metaclass_callback_called
-    end
-
-    def module_callback_called?
-      @module_callback_called ||= false
-    end
-
-    def raise_metaclass_callback_called
-      @module_callback_called = true
-    end
-  end
-
-  def test_metaclass_callbacks
-    person = Person.new
-    person.extend(ModuleWithCallbacks)
-    assert !person.module_callback_called?
-    person.save
-    assert person.module_callback_called?
-  end
-end
-
 class ConditionalCallbackTest < Test::Unit::TestCase
   def test_save_conditional_person
     person = ConditionalPerson.new