rails/rails — pull request #8072 by kennyj (2012-10-30 14:51:31+00:00)
Title: include_root_in_json attribute should be class_attribute.

When I executed rails's testcases, I found the following warnings. And I wanted to fix this.

```
activesupport/lib/active_support/core_ext/module/attribute_accessors.rb:11: warning: method redefined; discarding old include_root_in_json
activesupport/lib/active_support/core_ext/class/attribute.rb:83: warning: previous definition of include_root_in_json was here
activesupport/lib/active_support/core_ext/module/attribute_accessors.rb:31: warning: method redefined; discarding old include_root_in_json=
activesupport/lib/active_support/core_ext/class/attribute.rb:80: warning: previous definition of include_root_in_json= was here
```

But I thought `include_root_in_json` should be `class_attribute` (inheritanceable attribute), and my testcase was not passed.