Backed out changeset aaa160599ef4 (bug 1561773) for causing tab leaks on a CLOSED TREE

modules/libpref/init/StaticPrefList.h

@@ -4708,7 +4708,7 @@ VARCACHE_PREF(
   Live,
   "layout.css.cached-scrollbar-styles.enabled",
   layout_css_cached_scrollbar_styles_enabled,
-  bool, true
+  bool, false
 )
 
 // Is path() supported in clip-path?