More optimizations on respond_to after a profile and benching:

App with simple respond_to:
  def index
    respond_to do |format|
      format.html
      format.xml
      format.json
    end
  end

On JRuby (after complete hotspot warmup) -- 8% improvement:
  550 requests per second after this commit
  510 requests per second with old method_missing technique

On MRI (8% improvement):
  430 requests per second after this commit
  400 requests per second with old method_missing technique

actionpack/lib/action_controller/mime_responds.rb

@@ -147,13 +147,9 @@ def any(*args, &block)
       def self.generate_method_for_mime(mime)
         sym = mime.is_a?(Symbol) ? mime : mime.to_sym
         const = sym.to_s.upcase
-        class_eval <<-RUBY
+        class_eval <<-RUBY, __FILE__, __LINE__ + 1
           def #{sym}(&block)                          # def html(&block)
-            if Mime::SET.include?(Mime::#{const})     #   if Mime::Set.include?(Mime::HTML)
-              custom(Mime::#{const}, &block)          #     custom(Mime::HTML, &block)
-            else                                      #   else
-              super                                   #     super
-            end                                       #   end
+            custom(Mime::#{const}, &block)            #   custom(Mime::HTML, &block)
           end                                         # end
         RUBY
       end