Revert "Merge pull request #5995 from kennyj/fix_5847-3"

Active Record should be lazy loaded and this pull request
forced Active Record to always be loaded after initialization.

This reverts commit 8cd14c0bc9f9429f03d1181912355d2f48b98157, reversing
changes made to 2f0c8c52e66f1a2a3d1c00efc207f227124e96c2.

activerecord/lib/active_record/railtie.rb

@@ -128,10 +128,5 @@ class Railtie < Rails::Railtie
       end
 
     end
-
-    config.after_initialize do
-      # We should load ActiveRecord::Base class before loading an application model.
-      require "active_record/base"
-    end
   end
 end

railties/test/application/rake_test.rb

@@ -167,27 +167,5 @@ def test_rake_clear_schema_cache
       end
       assert !File.exists?(File.join(app_path, 'db', 'schema_cache.dump'))
     end
-
-    def test_load_activerecord_base_when_we_use_observers
-      Dir.chdir(app_path) do
-        `bundle exec rails g model user;
-         bundle exec rake db:migrate;
-         bundle exec rails g observer user;`
-
-        add_to_config "config.active_record.observers = :user_observer"
-
-        assert_equal "0", `bundle exec rails r "puts User.count"`.strip
-
-        app_file "lib/tasks/count_user.rake", <<-RUBY
-          namespace :user do
-            task :count => :environment do
-              puts User.count
-            end
-          end
-        RUBY
-
-        assert_equal "0", `bundle exec rake user:count`.strip
-      end
-    end
   end
 end