Remove stream at the class level.

This is because only template rendering works with streaming.
Setting it at the class level was also changing the behavior
of JSON and XML responses, closes #1337.

actionpack/lib/action_controller/metal/streaming.rb

@@ -24,20 +24,8 @@ module ActionController #:nodoc:
   #
   # == Examples
   #
-  # Streaming can be added to a controller easily, all you need to do is
+  # Streaming can be added to a given template easily, all you need to do is
-  # call +stream+ in the controller class:
+  # to pass the :stream option.
-  #
-  #   class PostsController
-  #     stream
-  #   end
-  #
-  # The +stream+ method accepts the same options as +before_filter+ and friends:
-  #
-  #   class PostsController
-  #     stream :only => :index
-  #   end
-  #
-  # You can also selectively turn on streaming for specific actions:
   #
   #   class PostsController
   #     def index
@@ -72,6 +60,9 @@ module ActionController #:nodoc:
   #     render :stream => true
   #   end
   #
+  # Notice that :stream only works with templates. Rendering :json
+  # or :xml with :stream won't work.
+  #
   # == Communication between layout and template
   #
   # When streaming, rendering happens top-down instead of inside-out.
@@ -209,33 +200,9 @@ module Streaming
     extend ActiveSupport::Concern
 
     include AbstractController::Rendering
-    attr_internal :stream
-
-    module ClassMethods
-      # Render streaming templates. It accepts :only, :except, :if and :unless as options
-      # to specify when to stream, as in ActionController filters.
-      def stream(options={})
-        if defined?(Fiber)
-          before_filter :_stream_filter, options
-        else
-          raise "You cannot use streaming if Fiber is not available."
-        end
-      end
-    end
 
     protected
 
-    # Mark following render calls as streaming.
-    def _stream_filter #:nodoc:
-      self.stream = true
-    end
-
-    # Consider the stream option when normalazing options.
-    def _normalize_options(options) #:nodoc:
-      super
-      options[:stream] = self.stream unless options.key?(:stream)
-    end
-
     # Set proper cache control and transfer encoding when streaming
     def _process_options(options) #:nodoc:
       super

actionpack/test/controller/new_base/render_streaming_test.rb

@@ -10,9 +10,9 @@ class BasicController < ActionController::Base
     )]
 
     layout "application"
-    stream :only => [:hello_world, :skip]
 
     def hello_world
+      render :stream => true
     end
 
     def layout_exception