servo: Merge #17046 - Fix stylo bindings for Gecko changes to nsITheme constants in bug 1367577 (from dbaron:bug1367577); r=Manishearth

These changes fix the stylo bindings for the changes to the Gecko nsITheme constants in [bug 1367577](https://bugzilla.mozilla.org/show_bug.cgi?id=1367577).

I believe there isn't anything in these changes that should affect the stylo build (as opposed to the servo build, which I've tested on try in that bug).

Source-Repo: https://github.com/servo/servo
Source-Revision: dbadf5a8b658214a30f2c24b444952962a4b97aa

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : d2acf0b9c55e2489ce65782dbc1891c44c630703

servo/components/style/properties/longhand/box.mako.rs

@@ -2340,7 +2340,7 @@ ${helpers.single_keyword("-moz-appearance",
                             -moz-window-titlebar-maximized
                          """,
                          gecko_ffi_name="mAppearance",
-                         gecko_constant_prefix="NS_THEME",
+                         gecko_constant_prefix="ThemeWidgetType_NS_THEME",
                          products="gecko",
                          spec="Nonstandard (https://developer.mozilla.org/en-US/docs/Web/CSS/-moz-appearance)",
                          animation_value_type="none")}