Fix memory leak in development mode

Keying these hashes by klass causes reloadable classes to never get
freed. Thanks to @thedarkone for pointing this out in
the comments on 221571beb6b4bb7437989bdefaf421f993ab6002.

This doesn't seem to make a massive difference to performance.

Benchmark
---------

require 'active_record'
require 'benchmark/ips'

class Post < ActiveRecord::Base
  establish_connection adapter: 'sqlite3', database: ':memory:'
end

GC.disable

Benchmark.ips(20) do |r|
  r.report { Post.connection }
end

Before
------

Calculating -------------------------------------
                          5632 i/100ms
-------------------------------------------------
                       218671.0 (±1.9%) i/s -    4364800 in  19.969401s

After
-----

Calculating -------------------------------------
                          8743 i/100ms
-------------------------------------------------
                       206525.9 (±17.8%) i/s -    4039266 in  19.992590s

1 files changed, 5 insertions, 7 deletions

diff --git a/activerecord/test/cases/connection_adapters/connection_handler_test.rb b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
index 2ddabe058f..3e33b30144 100644
--- a/activerecord/test/cases/connection_adapters/connection_handler_test.rb
+++ b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
@@ -4,8 +4,8 @@ module ActiveRecord
   module ConnectionAdapters
     class ConnectionHandlerTest < ActiveRecord::TestCase
       def setup
-        @klass    = Class.new(Base)
-        @subklass = Class.new(@klass)
+        @klass    = Class.new(Base)   { def self.name; 'klass';    end }
+        @subklass = Class.new(@klass) { def self.name; 'subklass'; end }
 
         @handler = ConnectionHandler.new
         @pool    = @handler.establish_connection(@klass, Base.connection_pool.spec)
@@ -36,13 +36,11 @@ module ActiveRecord
       end
 
       def test_retrieve_connection_pool_uses_superclass_pool_after_subclass_establish_and_remove
-        @handler.establish_connection 'north america', Base.connection_pool.spec
-        assert_same @handler.retrieve_connection_pool(@klass),
-          @handler.retrieve_connection_pool(@subklass)
+        sub_pool = @handler.establish_connection(@subklass, Base.connection_pool.spec)
+        assert_same sub_pool, @handler.retrieve_connection_pool(@subklass)
 
         @handler.remove_connection @subklass
-        assert_same @handler.retrieve_connection_pool(@klass),
-          @handler.retrieve_connection_pool(@subklass)
+        assert_same @pool, @handler.retrieve_connection_pool(@subklass)
       end
 
       def test_connection_pools