Enable experimental background color for staging.

(imported from commit 833b25ae48e44bc7749463b7dd26418d6e25703a)

static/js/feature_flags.js

@@ -47,6 +47,8 @@ exports.use_socket = false;
 exports.clicking_notification_causes_narrow = page_params.staging || is_customer4 ||
     _.contains(['customer25.invalid'], page_params.domain);
 
+exports.experimental_background = page_params.staging;
+
 exports.show_digest_email_setting = page_params.staging;
 
 var zoom_realms = [

static/js/ui.js

@@ -1619,6 +1619,11 @@ $(function () {
         $("#group-pm-list").hide();
     }
 
+    // UI experiments
+    if (feature_flags.experimental_background) {
+        exports.switchBackground();
+    }
+
     // initialize other stuff
     composebox_typeahead.initialize();
     search.initialize();