* It is not possible to always pre-determine the layout before going to ActionView.
This was *already* broken for render :partial => @object, :layout => true. This is
now handled by overriding render_to_body in layouts.rb and manually injecting the
partial's response. This needs to be done in ActionController since ActionController
knows enough to get _layout_for_option. There is probably a better abstraction here.
* As a result, all partial rendering can correctly restrict their layouts to the mime
type of the rendered partial. This could have previously caused a bug in some edge cases.
* If other layout-like options are added, they might need to add special code for the
case of render :partial. We should try to think of an alternate solution, if possible,
but this works for the cases we know of now.
