@osheroff, I'm not sure if I get what do you want to inject?

I think that `superclass` is never called because `pool_for` method ultimately fetches data from @owner_to_pool variable and if our connection pool names are not there, there is nothing what we can do about it but raise ConnectionNotEstablished. It looks like Rails 4 assumes that there is always a key for ActiveRecord::Base in @owner_to_pool

```shell
Loading development environment (Rails 4.0.0)
2.0.0-p247 :001 > ActiveRecord::Base.connection_handler.send(:owner_to_pool).keys
 => ["ActiveRecord::Base"]
2.0.0-p247 :002 > Account.all
  Account Load (0.1ms)  SELECT "accounts".* FROM "accounts"
 => #<ActiveRecord::Relation []>
2.0.0-p247 :003 > ActiveRecord::Base.connection_handler.remove_connection(ActiveRecord::Base)
 => {:adapter=>"sqlite3", :database=>"/Users/lukkry/projects/mango_test/db/development.sqlite3", :pool=>5, :timeout=>5000}
2.0.0-p247 :004 > Account.all
ActiveRecord::ConnectionNotEstablished: ActiveRecord::ConnectionNotEstablished
        from /Users/lukkry/.rvm/gems/ruby-2.0.0-p247/gems/activerecord-4.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:546:in `retrieve_connection'
        from /Users/lukkry/.rvm/gems/ruby-2.0.0-p247/gems/activerecord-4.0.0/lib/active_record/connection_handling.rb:79:in `retrieve_connection'
        from /Users/lukkry/.rvm/gems/ruby-2.0.0-p247/gems/activerecord-4.0.0/lib/active_record/connection_handling.rb:53:in `connection'
        from /Users/lukkry/.rvm/gems/ruby-2.0.0-p247/gems/activerecord-4.0.0/lib/active_record/querying.rb:36:in `find_by_sql'
        from /Users/lukkry/.rvm/gems/ruby-2.0.0-p247/gems/activerecord-4.0.0/lib/active_record/relation.rb:585:in `exec_queries'
        from /Users/lukkry/.rvm/gems/ruby-2.0.0-p247/gems/activerecord-4.0.0/lib/active_record/relation.rb:471:in `load'
        from /Users/lukkry/.rvm/gems/ruby-2.0.0-p247/gems/activerecord-4.0.0/lib/active_record/relation.rb:220:in `to_a'
        from /Users/lukkry/.rvm/gems/ruby-2.0.0-p247/gems/activerecord-4.0.0/lib/active_record/relation.rb:573:in `inspect'
        from /Users/lukkry/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.0/lib/rails/commands/console.rb:90:in `start'
        from /Users/lukkry/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.0/lib/rails/commands/console.rb:9:in `start'
        from /Users/lukkry/.rvm/gems/ruby-2.0.0-p247/gems/railties-4.0.0/lib/rails/commands.rb:64:in `<top (required)>'
        from bin/rails:4:in `require'
        from bin/rails:4:in `<main>'
```

so it should be safe to assume that there is always a key for our connection pool name.