remove AV.prepare and move all helper-related logic into the controller. this...

remove AV.prepare and move all helper-related logic into the controller. this decouples the view since it no longer knows about routes internals.
this is a result of an ongoing discussion at https://github.com/rails/rails/pull/6826.

actionpack/lib/abstract_controller/rendering.rb

@@ -49,9 +49,19 @@ def process(*) #:nodoc:
     module ClassMethods
       def view_context_class
         @view_context_class ||= begin
-          routes  = _routes  if respond_to?(:_routes)
-          helpers = _helpers if respond_to?(:_helpers)
-          ActionView::Base.prepare(routes, helpers)
+          routes = respond_to?(:_routes) && _routes
+          helpers = respond_to?(:_helpers) && _helpers
+          
+          Class.new(ActionView::Base) do
+            if routes
+              include routes.url_helpers
+              include routes.mounted_helpers
+            end
+
+            if helpers
+              include helpers
+            end
+          end
         end
       end
     end

actionpack/lib/action_view/base.rb

@@ -166,22 +166,6 @@ def cache_template_loading=(value)
       def xss_safe? #:nodoc:
         true
       end
-
-      # This method receives routes and helpers from the controller
-      # and return a subclass ready to be used as view context.
-      def prepare(routes, helpers) #:nodoc:
-        Class.new(self) do
-          if routes
-            include routes.url_helpers
-            include routes.mounted_helpers
-          end
-
-          if helpers
-            include helpers
-            self.helpers = helpers
-          end
-        end
-      end
     end
 
     attr_accessor :view_renderer