Pull `plain` content type handling up to `render`

`render` is the only possible source for the `plain` option.  Pulling
the conditional up to the `render` method removes far away conditionals

1 files changed, 1 insertions, 1 deletions

diff --git a/actionview/lib/action_view/rendering.rb b/actionview/lib/action_view/rendering.rb
index f63c397c5b..8604637da2 100644
--- a/actionview/lib/action_view/rendering.rb
+++ b/actionview/lib/action_view/rendering.rb
@@ -104,7 +104,7 @@ module ActionView
       end
 
       # Assign the rendered format to look up context.
-      def _process_format(format, plain = false) #:nodoc:
+      def _process_format(format) #:nodoc:
         super
         lookup_context.formats = [format.to_sym]
         lookup_context.rendered_format = lookup_context.formats.first