Remove dependent destroy circular dependency

rails/rails#13609

Having dependent: :destroy on both the question_content and
survey_element for the assetable polymorphic belongs_to causes a
loop in the destroy callbacks for rails 4.0

Removing the dependent :destroy solves the issue for 4.0, but they
should be added back in for the move to rails 4.1 as the issue is fixed
in rails.

rails/rails#18548

app/models/question_models/question_content.rb

@@ -3,7 +3,7 @@
 # QuestionContent contains fields shared between all question types (ChoiceQuestion,
 # TextQuestion, MatrixQuestion) and delegates behavior where appropriate.
 class QuestionContent < ActiveRecord::Base
-  belongs_to :questionable, :polymorphic => true, :dependent => :destroy
+  belongs_to :questionable, :polymorphic => true#, :dependent => :destroy
   has_many :criteria, :as => :source
   has_many :raw_responses, :foreign_key => "question_content_id" # likely currently unused. had a typo
   has_many :question_content_display_fields

app/models/survey_models/survey_element.rb

@@ -4,7 +4,7 @@
 # which exists on a Page within a SurveyVersion.
 class SurveyElement < ActiveRecord::Base
   belongs_to :page
-  belongs_to :assetable, :polymorphic => true, :dependent => :destroy
+  belongs_to :assetable, :polymorphic => true#, :dependent => :destroy
   belongs_to :survey_version, :touch => true
   has_many :dashboard_elements, :dependent => :destroy
 

spec/features/survey_builder_spec.rb

@@ -17,6 +17,17 @@
       add_text_question statement: ""
       expect(page).to_not have_css ".page_asset"
     end
+
+    scenario "User deletes a text question" do
+      survey = create :survey
+      login_user
+      visit edit_survey_survey_version_path(survey, survey.survey_versions.first)
+      add_text_question statement: "Example Question"
+      within find('div.page_asset', text: "Example Question") do
+        click_link "Delete"
+      end
+      expect(page).to_not have_css ".page_asset", text: "Example Question"
+    end
   end
 
   context "choice question" do