MAGETWO-57118: [github#6201] Form key shared between admin and frontend

app/code/Magento/PageCache/etc/events.xml

@@ -48,11 +48,6 @@
     <event name="model_save_commit_after">
         <observer name="flush_cache_after_model_save" instance="Magento\PageCache\Observer\FlushCacheByTags" />
     </event>
-    <event name="controller_action_predispatch">
-        <observer name="register_form_key"
-                  instance="Magento\PageCache\Observer\RegisterFormKeyFromCookie"
-                  />
-    </event>
     <event name="customer_logout">
         <observer name="FlushFormKeyOnLogout" instance="Magento\PageCache\Observer\FlushFormKeyOnLogout"/>
     </event>

app/code/Magento/PageCache/etc/frontend/events.xml

+<?xml version="1.0"?>
+<!--
+/**
+ * Copyright © 2016 Magento. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+-->
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
+    <event name="controller_action_predispatch">
+        <observer name="register_form_key" instance="Magento\PageCache\Observer\RegisterFormKeyFromCookie" />
+    </event>
+</config>