Use as_json instead of rails_to_json

actionpack/lib/action_view/helpers/prototype_helper.rb

@@ -1176,7 +1176,7 @@ module ActionView
 
     class JavaScriptVariableProxy < JavaScriptProxy #:nodoc:
       def initialize(generator, variable)
-        @variable = variable
+        @variable = ActiveSupport::JSON::Variable.new(variable)
         @empty    = true # only record lines if we have to.  gets rid of unnecessary linebreaks
         super(generator)
       end
@@ -1187,7 +1187,7 @@ module ActionView
         true
       end
 
-      def rails_to_json(*)
+      def as_json(options = nil)
         @variable
       end