Bug 1579608 - temporarily set pref csp.skip_about_page_has_csp_assert. rs=bustage-fix

mail/app/profile/all-thunderbird.js

@@ -355,6 +355,12 @@ pref("network.hosts.pop_server",            "mail");
 // The list should be kept in sync with the one in m-c/modules/libpref/init/all.js. See bug 1495983.
 pref("csp.about_uris_without_csp", "preferences,newserror,blank,printpreview,srcdoc,about,addons,cache-entry,config,crashes,debugging,devtools,downloads,home,memory,networking,newtab,performance,policies,profiles,restartrequired,searchreset,serviceworkers,sessionrestore,support,sync-log,telemetry,url-classifier,webrtc,welcomeback");
 
+#if defined(DEBUG)
+  // For testing purposes only: Flipping this pref to true allows
+  // to skip the assertion that every about page ships with a CSP.
+  pref("csp.skip_about_page_has_csp_assert", true);
+#endif
+
 pref("security.warn_entering_secure", false);
 pref("security.warn_entering_weak", false);
 pref("security.warn_leaving_secure", false);