Remove description for screen readers

It was being duplicated when restoring a page by using browser
history. With this solution we will avoid to have screen readers
descriptions more than once inside any sociual share button.

app/assets/javascripts/application.js

@@ -173,6 +173,7 @@ var destroy_non_idempotent_modules = function() {
   App.Datepicker.destroy();
   App.HTMLEditor.destroy();
   App.LegislationAnnotatable.destroy();
+  App.SocialShare.destroy();
 };
 
 $(document).on("turbolinks:load", initialize_modules);

app/assets/javascripts/social_share.js

@@ -5,6 +5,9 @@
       $(".social-share-button a").each(function() {
         $(this).append("<span class='show-for-sr'>" + ($(this).data("site")) + "</span>");
       });
+    },
+    destroy: function() {
+      $(".social-share-button a .show-for-sr").remove();
     }
   };
 }).call(this);

spec/system/proposals_spec.rb

@@ -198,6 +198,18 @@ describe "Proposals" do
         expect(page).not_to have_link("No comments", href: "#comments")
       end
     end
+
+    scenario "After using the browser's back button, social buttons will have one screen reader", :js do
+      proposal = create(:proposal)
+      visit proposal_path(proposal)
+      click_link "Help"
+
+      expect(page).to have_content "CONSUL is a platform for citizen participation"
+
+      go_back
+
+      expect(page).to have_css "span.show-for-sr", text: "twitter", count: 1
+    end
   end
 
   describe "Show sticky support button on mobile screens", :js do