stop passing params to array_of_permitted_scalars_filter

this way the method doesn't have to know what the new params object is,
it just yields to a block.  This change also caches the value of
`self[key]` on the stack

Author: tenderlove

actionpack/lib/action_controller/metal/strong_parameters.rb

@@ -648,9 +648,9 @@ def array_of_permitted_scalars?(value)
         end
       end
 
-      def array_of_permitted_scalars_filter(params, key)
-        if array_of_permitted_scalars?(self[key])
-          params[key] = self[key]
+      def array_of_permitted_scalars_filter(value)
+        if array_of_permitted_scalars?(value)
+          yield value
         end
       end
 
@@ -665,7 +665,9 @@ def hash_filter(params, filter)
 
           if filter[key] == EMPTY_ARRAY
             # Declaration { comment_ids: [] }.
-            array_of_permitted_scalars_filter(params, key)
+            array_of_permitted_scalars_filter(self[key]) do |val|
+              params[key] = val
+            end
           else
             # Declaration { user: :name } or { user: [:name, :age, { address: ... }] }.
             params[key] = each_element(value) do |element|