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, 2 insertions, 6 deletions

diff --git a/actionpack/lib/action_controller/metal/rendering.rb b/actionpack/lib/action_controller/metal/rendering.rb
index 0a005085ba..a2d671486d 100644
--- a/actionpack/lib/action_controller/metal/rendering.rb
+++ b/actionpack/lib/action_controller/metal/rendering.rb
@@ -56,14 +56,10 @@ module ActionController
       nil
     end
 
-    def _process_format(format, plain = false)
+    def _process_format(format)
       super
 
-      if plain
-        self.content_type = Mime::TEXT
-      else
-        self.content_type ||= format.to_s
-      end
+      self.content_type ||= format.to_s
     end
 
     # Normalize arguments by catching blocks and setting them on :update.