Rename isolated_engine_for to namespace

railties/lib/rails/engine.rb

@@ -200,11 +200,11 @@ module Rails
         @endpoint
       end
 
-      def isolated_engine_for(mod)
-        _engine = self
+      def namespace(mod)
+        _railtie = self
         mod.singleton_class.instance_eval do
           define_method(:_railtie) do
-            _engine
+            _railtie
           end
         end
       end

railties/test/railties/engine_test.rb

@@ -338,11 +338,11 @@ module RailtiesTest
       assert_equal "/foo", response[2].body
     end
 
-    test "isolated engine should include only its own routes and helpers" do
+    test "namespaced engine should include only its own routes and helpers" do
       @plugin.write "lib/bukkits.rb", <<-RUBY
         module Bukkits
           class Engine < ::Rails::Engine
-            isolated_engine_for Bukkits
+            namespace Bukkits
           end
         end
       RUBY