Bug 1567352 - Whitelist about:devtools-toolbox for not having CSP yet. r=ckerschb

When about:devtools-toolbox is loaded as XHTML the CSP assertion triggers.

Differential Revision: https://phabricator.services.mozilla.com/D38595

--HG--
extra : moz-landing-system : lando

modules/libpref/init/all.js

@@ -2448,7 +2448,7 @@ pref("security.dialog_enable_delay", 1000);
 pref("security.notification_enable_delay", 500);
 
 #if defined(DEBUG) && !defined(ANDROID)
-pref("csp.about_uris_without_csp", "blank,printpreview,srcdoc,addons,config,downloads,home,newtab,preferences,sync-log");
+pref("csp.about_uris_without_csp", "blank,printpreview,srcdoc,devtools-toolbox,addons,config,downloads,home,newtab,preferences,sync-log");
 // the following prefs are for testing purposes only.
 pref("csp.overrule_about_uris_without_csp_whitelist", false);
 pref("csp.skip_about_page_has_csp_assert", false);