This resolves the following error:

```
Error:
TestAdapterWithInvalidConnection#test_inspect_on_Model_class_does_not_raise:
TypeError: superclass mismatch for class Mysql2Adapter
    /Users/senny/Projects/rails/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb:35:in `<module:ConnectionAdapters>'
    /Users/senny/Projects/rails/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb:34:in `<module:ActiveRecord>'
    /Users/senny/Projects/rails/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb:6:in `<top (required)>'
    /Users/senny/Projects/rails/activesupport/lib/active_support/dependencies.rb:302:in `require'
    /Users/senny/Projects/rails/activesupport/lib/active_support/dependencies.rb:302:in `block in require'
    /Users/senny/Projects/rails/activesupport/lib/active_support/dependencies.rb:268:in `load_dependency'
    /Users/senny/Projects/rails/activesupport/lib/active_support/dependencies.rb:302:in `require'
    /Users/senny/Projects/rails/activerecord/lib/active_record/connection_adapters/connection_specification.rb:174:in `spec'
    /Users/senny/Projects/rails/activerecord/lib/active_record/connection_handling.rb:50:in `establish_connection'
    /Users/senny/Projects/rails/activerecord/test/cases/invalid_connection_test.rb:12:in `setup'
```