inherit from the new ActiveSupport::BlankSlate class

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8501 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activeresource/test/setter_trap.rb

-class SetterTrap < BasicObject
+class SetterTrap < ActiveSupport::BasicObject
   class << self
     def rollback_sets(obj)
       returning yield(setter_trap = new(obj)) do