This change causes some failing tests, but it should be possible to make them pass with minimal performance impact.

actionpack/examples/minimal.rb

@@ -91,6 +91,8 @@ class HttpPostController < ActionController::Metal
   end
 end
 
+ActionController::Base.use_accept_header = false
+
 unless ENV["PROFILE"]
   Runner.run(BasePostController.action(:overhead), N, 'overhead', false)
   Runner.run(BasePostController.action(:index), N, 'index', false)
@@ -108,10 +110,10 @@ unless ENV["PROFILE"]
     Runner.run(BasePostController.action(:show_template), N, 'template')
   end
 else
-  Runner.run(BasePostController.action(:many_partials), N, 'many_partials')
+  Runner.run(BasePostController.action(ENV["PROFILE"].to_sym), N, ENV["PROFILE"])
   require "ruby-prof"
   RubyProf.start
-  Runner.run(BasePostController.action(:many_partials), N, 'many_partials')
+  Runner.run(BasePostController.action(ENV["PROFILE"].to_sym), N, ENV["PROFILE"])
   result = RubyProf.stop
   printer = RubyProf::CallStackPrinter.new(result)
   printer.print(File.open("output.html", "w"))

actionpack/lib/action_dispatch/http/request.rb

@@ -176,17 +176,18 @@ module ActionDispatch
     # Expand raw_formats by converting Mime::ALL to the Mime::SET.
     #
     def formats
-      if ActionController::Base.use_accept_header
-        raw_formats.tap do |ret|
-          if ret == ONLY_ALL
-            ret.replace Mime::SET
-          elsif all = ret.index(Mime::ALL)
-            ret.delete_at(all) && ret.insert(all, *Mime::SET)
-          end
-        end
-      else
-        raw_formats + Mime::SET
-      end
+      return raw_formats
+      # if ActionController::Base.use_accept_header
+      #   raw_formats.tap do |ret|
+      #     if ret == ONLY_ALL
+      #       ret.replace Mime::SET
+      #     elsif all = ret.index(Mime::ALL)
+      #       ret.delete_at(all) && ret.insert(all, *Mime::SET)
+      #     end
+      #   end
+      # else
+      #   raw_formats + Mime::SET
+      # end
     end
 
     # Sets the \format by string extension, which can be used to force custom formats

actionpack/lib/action_view/template/resolver.rb

@@ -41,8 +41,10 @@ module ActionView
     end
 
     def handler_glob
-      e = TemplateHandlers.extensions.map{|h| ".#{h},"}.join
-      "{#{e}}"
+      @handler_glob ||= begin
+        e = TemplateHandlers.extensions.map{|h| ".#{h},"}.join
+        "{#{e}}"
+      end
     end
     
     def formats_glob