Merge pull request #5101 from ckdake/ckdake_actionview_handler_reset

Reset memoized hash keys when new ActionView::Template handler is registered
Conflicts:

	actionpack/lib/action_view/template/handlers.rb

actionpack/lib/action_view/template/handlers.rb

@@ -23,6 +23,7 @@ def self.extensions
       # and should return the rendered template as a String.
       def register_template_handler(extension, handler)
         @@template_handlers[extension.to_sym] = handler
+        @@template_extensions = nil
       end
 
       def template_handler_extensions

actionpack/test/template/render_test.rb

@@ -299,6 +299,12 @@ def test_render_inline_with_locals_and_compilable_custom_type
     ActionView::Template.register_template_handler :foo, CustomHandler
     assert_equal 'source: "Hello, <%= name %>!"', @view.render(:inline => "Hello, <%= name %>!", :locals => { :name => "Josh" }, :type => :foo)
   end
+  
+  def test_render_knows_about_types_registered_when_extensions_are_checked_earlier_in_initialization
+    ActionView::Template::Handlers.extensions
+    ActionView::Template.register_template_handler :foo, CustomHandler
+    assert ActionView::Template::Handlers.extensions.include?(:foo)
+  end
 
   def test_render_ignores_templates_with_malformed_template_handlers
     ActiveSupport::Deprecation.silence do