Bug 842329 - Part 0: Add "layout.css.all-shorthand.enabled" pref. r=bzbarsky

modules/libpref/src/init/all.js

@@ -1903,6 +1903,9 @@ pref("layout.css.osx-font-smoothing.enabled", false);
 // Is support for the CSS-wide "unset" value enabled?
 pref("layout.css.unset-value.enabled", true);
 
+// Is support for the "all" shorthand enabled?
+pref("layout.css.all-shorthand.enabled", true);
+
 // pref for which side vertical scrollbars should be on
 // 0 = end-side in UI direction
 // 1 = end-side in document/content direction