Deprecate 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
-  # call +stream+ in the controller class:
-  #
-  #   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:
+  # Streaming can be added to a given template easily, all you need to do is
+  # to pass the :stream option.
   #
   #   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.
@@ -215,6 +206,7 @@ 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={})
+        ActiveSupport::Deprecation.warn "stream class method is deprecated. Please give the :stream option to render instead"
         if defined?(Fiber)
           before_filter :_stream_filter, options
         else

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