Bug 855455: Turn on @supports in release builds. r=heycam

Author: dbaron

modules/libpref/src/init/all.js

@@ -1702,11 +1702,7 @@ pref("layout.css.masking.enabled", true);
 #endif
 
 // Is support for the the @supports rule enabled?
-#ifdef RELEASE_BUILD
-pref("layout.css.supports-rule.enabled", false);
-#else
 pref("layout.css.supports-rule.enabled", true);
-#endif
 
 // Is support for CSS Flexbox enabled?
 pref("layout.css.flexbox.enabled", true);