--- a/layout/style/crashtests/crashtests.list
+++ b/layout/style/crashtests/crashtests.list
@@ -113,18 +113,18 @@ load 972199-1.html
 load 989965-1.html
 load 992333-1.html
 pref(dom.webcomponents.shadowdom.enabled,true) load 1017798-1.html
 load 1028514-1.html
 load 1066089-1.html
 load 1074651-1.html
 load 1135534.html
 pref(dom.webcomponents.shadowdom.enabled,true) load 1089463-1.html
-pref(layout.css.expensive-style-struct-assertions.enabled,true) load 1136010-1.html
-pref(layout.css.expensive-style-struct-assertions.enabled,true) load 1146101-1.html
+load 1136010-1.html
+load 1146101-1.html
 load 1153693-1.html
 load 1161320-1.html
 pref(dom.animations-api.core.enabled,true) load 1161320-2.html
 load 1161366-1.html
 load 1163446-1.html
 load 1164813-1.html
 load 1167782-1.html
 load 1186768-1.xhtml

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -5257,21 +5257,16 @@ pref("media.ondevicechange.fakeDeviceCha
 
 // W3C touch-action css property (related to touch and pointer events)
 // Note that we turn this on even on platforms/configurations where touch
 // events are not supported (e.g. OS X, or Windows with e10s disabled). For
 // those platforms we don't handle touch events anyway so it's conceptually
 // a no-op.
 pref("layout.css.touch_action.enabled", true);
 
-// Enables some assertions in ComputedStyle that are too expensive
-// for general use, but might be useful to enable for specific tests.
-// This only has an effect in DEBUG-builds.
-pref("layout.css.expensive-style-struct-assertions.enabled", false);
-
 #if defined(MOZ_WIDGET_ANDROID)
 // Network Information API
 pref("dom.netinfo.enabled", true);
 #else
 pref("dom.netinfo.enabled", false);
 #endif
 
 // How long must we wait before declaring that a window is a "ghost" (i.e., a