--- a/layout/style/nsStyleConsts.h
+++ b/layout/style/nsStyleConsts.h
@@ -1056,16 +1056,27 @@ enum class StyleGridTrackBreadth : uint8
 #define NS_STYLE_GRADIENT_SIZE_EXPLICIT_SIZE    4
 
 // See nsStyleSVG
 
 // -moz-context-properties
 #define NS_STYLE_CONTEXT_PROPERTY_FILL          (1 << 0)
 #define NS_STYLE_CONTEXT_PROPERTY_STROKE        (1 << 1)
 
+/*
+ * -moz-window-shadow
+ * Also used in widget code
+ */
+
+#define NS_STYLE_WINDOW_SHADOW_NONE             0
+#define NS_STYLE_WINDOW_SHADOW_DEFAULT          1
+#define NS_STYLE_WINDOW_SHADOW_MENU             2
+#define NS_STYLE_WINDOW_SHADOW_TOOLTIP          3
+#define NS_STYLE_WINDOW_SHADOW_SHEET            4
+
 // dominant-baseline
 #define NS_STYLE_DOMINANT_BASELINE_AUTO              0
 #define NS_STYLE_DOMINANT_BASELINE_USE_SCRIPT        1
 #define NS_STYLE_DOMINANT_BASELINE_NO_CHANGE         2
 #define NS_STYLE_DOMINANT_BASELINE_RESET_SIZE        3
 #define NS_STYLE_DOMINANT_BASELINE_IDEOGRAPHIC       4
 #define NS_STYLE_DOMINANT_BASELINE_ALPHABETIC        5
 #define NS_STYLE_DOMINANT_BASELINE_HANGING           6

--- a/servo/components/style/gecko/generated/structs_debug.rs
+++ b/servo/components/style/gecko/generated/structs_debug.rs
@@ -801,16 +801,21 @@ pub mod root {
     pub const NS_STYLE_GRADIENT_SIZE_FARTHEST_SIDE: ::std::os::raw::c_uint =
         2;
     pub const NS_STYLE_GRADIENT_SIZE_FARTHEST_CORNER: ::std::os::raw::c_uint =
         3;
     pub const NS_STYLE_GRADIENT_SIZE_EXPLICIT_SIZE: ::std::os::raw::c_uint =
         4;
     pub const NS_STYLE_CONTEXT_PROPERTY_FILL: ::std::os::raw::c_uint = 1;
     pub const NS_STYLE_CONTEXT_PROPERTY_STROKE: ::std::os::raw::c_uint = 2;
+    pub const NS_STYLE_WINDOW_SHADOW_NONE: ::std::os::raw::c_uint = 0;
+    pub const NS_STYLE_WINDOW_SHADOW_DEFAULT: ::std::os::raw::c_uint = 1;
+    pub const NS_STYLE_WINDOW_SHADOW_MENU: ::std::os::raw::c_uint = 2;
+    pub const NS_STYLE_WINDOW_SHADOW_TOOLTIP: ::std::os::raw::c_uint = 3;
+    pub const NS_STYLE_WINDOW_SHADOW_SHEET: ::std::os::raw::c_uint = 4;
     pub const NS_STYLE_DOMINANT_BASELINE_AUTO: ::std::os::raw::c_uint = 0;
     pub const NS_STYLE_DOMINANT_BASELINE_USE_SCRIPT: ::std::os::raw::c_uint =
         1;
     pub const NS_STYLE_DOMINANT_BASELINE_NO_CHANGE: ::std::os::raw::c_uint =
         2;
     pub const NS_STYLE_DOMINANT_BASELINE_RESET_SIZE: ::std::os::raw::c_uint =
         3;
     pub const NS_STYLE_DOMINANT_BASELINE_IDEOGRAPHIC: ::std::os::raw::c_uint =
@@ -34449,26 +34454,26 @@ pub mod root {
                    "Size of template specialization: " , stringify ! (
                    root::nsCharTraits ) ));
         assert_eq!(::std::mem::align_of::<root::nsCharTraits>() , 1usize ,
                    concat ! (
                    "Alignment of template specialization: " , stringify ! (
                    root::nsCharTraits ) ));
     }
     #[test]
-    fn __bindgen_test_layout__bindgen_ty_id_185241_instantiation_32() {
+    fn __bindgen_test_layout__bindgen_ty_id_185251_instantiation_32() {
         assert_eq!(::std::mem::size_of::<u8>() , 1usize , concat ! (
                    "Size of template specialization: " , stringify ! ( u8 )
                    ));
         assert_eq!(::std::mem::align_of::<u8>() , 1usize , concat ! (
                    "Alignment of template specialization: " , stringify ! ( u8
                    ) ));
     }
     #[test]
-    fn __bindgen_test_layout__bindgen_ty_id_185277_instantiation_33() {
+    fn __bindgen_test_layout__bindgen_ty_id_185287_instantiation_33() {
         assert_eq!(::std::mem::size_of::<u8>() , 1usize , concat ! (
                    "Size of template specialization: " , stringify ! ( u8 )
                    ));
         assert_eq!(::std::mem::align_of::<u8>() , 1usize , concat ! (
                    "Alignment of template specialization: " , stringify ! ( u8
                    ) ));
     }
     #[test]

--- a/servo/components/style/gecko/generated/structs_release.rs
+++ b/servo/components/style/gecko/generated/structs_release.rs
@@ -801,16 +801,21 @@ pub mod root {
     pub const NS_STYLE_GRADIENT_SIZE_FARTHEST_SIDE: ::std::os::raw::c_uint =
         2;
     pub const NS_STYLE_GRADIENT_SIZE_FARTHEST_CORNER: ::std::os::raw::c_uint =
         3;
     pub const NS_STYLE_GRADIENT_SIZE_EXPLICIT_SIZE: ::std::os::raw::c_uint =
         4;
     pub const NS_STYLE_CONTEXT_PROPERTY_FILL: ::std::os::raw::c_uint = 1;
     pub const NS_STYLE_CONTEXT_PROPERTY_STROKE: ::std::os::raw::c_uint = 2;
+    pub const NS_STYLE_WINDOW_SHADOW_NONE: ::std::os::raw::c_uint = 0;
+    pub const NS_STYLE_WINDOW_SHADOW_DEFAULT: ::std::os::raw::c_uint = 1;
+    pub const NS_STYLE_WINDOW_SHADOW_MENU: ::std::os::raw::c_uint = 2;
+    pub const NS_STYLE_WINDOW_SHADOW_TOOLTIP: ::std::os::raw::c_uint = 3;
+    pub const NS_STYLE_WINDOW_SHADOW_SHEET: ::std::os::raw::c_uint = 4;
     pub const NS_STYLE_DOMINANT_BASELINE_AUTO: ::std::os::raw::c_uint = 0;
     pub const NS_STYLE_DOMINANT_BASELINE_USE_SCRIPT: ::std::os::raw::c_uint =
         1;
     pub const NS_STYLE_DOMINANT_BASELINE_NO_CHANGE: ::std::os::raw::c_uint =
         2;
     pub const NS_STYLE_DOMINANT_BASELINE_RESET_SIZE: ::std::os::raw::c_uint =
         3;
     pub const NS_STYLE_DOMINANT_BASELINE_IDEOGRAPHIC: ::std::os::raw::c_uint =
@@ -33977,26 +33982,26 @@ pub mod root {
                    "Size of template specialization: " , stringify ! (
                    root::nsCharTraits ) ));
         assert_eq!(::std::mem::align_of::<root::nsCharTraits>() , 1usize ,
                    concat ! (
                    "Alignment of template specialization: " , stringify ! (
                    root::nsCharTraits ) ));
     }
     #[test]
-    fn __bindgen_test_layout__bindgen_ty_id_182965_instantiation_32() {
+    fn __bindgen_test_layout__bindgen_ty_id_182975_instantiation_32() {
         assert_eq!(::std::mem::size_of::<u8>() , 1usize , concat ! (
                    "Size of template specialization: " , stringify ! ( u8 )
                    ));
         assert_eq!(::std::mem::align_of::<u8>() , 1usize , concat ! (
                    "Alignment of template specialization: " , stringify ! ( u8
                    ) ));
     }
     #[test]
-    fn __bindgen_test_layout__bindgen_ty_id_183001_instantiation_33() {
+    fn __bindgen_test_layout__bindgen_ty_id_183011_instantiation_33() {
         assert_eq!(::std::mem::size_of::<u8>() , 1usize , concat ! (
                    "Size of template specialization: " , stringify ! ( u8 )
                    ));
         assert_eq!(::std::mem::align_of::<u8>() , 1usize , concat ! (
                    "Alignment of template specialization: " , stringify ! ( u8
                    ) ));
     }
     #[test]

--- a/servo/components/style/properties/longhand/ui.mako.rs
+++ b/servo/components/style/properties/longhand/ui.mako.rs
@@ -26,16 +26,23 @@
                          spec="https://drafts.csswg.org/css-ui-4/#propdef-user-select")}
 
 ${helpers.single_keyword("-moz-window-dragging", "default drag no-drag", products="gecko",
                          gecko_ffi_name="mWindowDragging",
                          gecko_enum_prefix="StyleWindowDragging",
                          animation_value_type="none",
                          spec="None (Nonstandard Firefox-only property)")}
 
+${helpers.single_keyword("-moz-window-shadow", "none default menu tooltip sheet", products="gecko",
+                         gecko_ffi_name="mWindowShadow",
+                         gecko_constant_prefix="NS_STYLE_WINDOW_SHADOW",
+                         animation_value_type="none",
+                         internal=True,
+                         spec="None (Nonstandard internal property)")}
+
 <%helpers:longhand name="-moz-force-broken-image-icon"
                    products="gecko"
                    animation_value_type="none"
                    spec="None (Nonstandard Firefox-only property)">
     use std::fmt;
     use style_traits::ToCss;
     use values::computed::ComputedValueAsSpecified;
 

--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -13,16 +13,17 @@
 #include "nsStringGlue.h"
 
 #include "nsCOMPtr.h"
 #include "nsWidgetInitData.h"
 #include "nsTArray.h"
 #include "nsITheme.h"
 #include "nsITimer.h"
 #include "nsRegionFwd.h"
+#include "nsStyleConsts.h"
 #include "nsXULAppAPI.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/EventForwards.h"
 #include "mozilla/layers/LayersTypes.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/TimeStamp.h"
 #include "mozilla/gfx/Point.h"
 #include "mozilla/widget/IMEData.h"
@@ -143,26 +144,16 @@ typedef void* nsNativeWidget;
 #define NS_PRESENTATION_WINDOW         101
 #define NS_PRESENTATION_SURFACE        102
 #endif
 
 #define NS_IWIDGET_IID \
 { 0x06396bf6, 0x2dd8, 0x45e5, \
   { 0xac, 0x45, 0x75, 0x26, 0x53, 0xb1, 0xc9, 0x80 } }
 
-/*
- * Window shadow styles
- * Also used for the -moz-window-shadow CSS property
- */
-
-#define NS_STYLE_WINDOW_SHADOW_NONE             0
-#define NS_STYLE_WINDOW_SHADOW_DEFAULT          1
-#define NS_STYLE_WINDOW_SHADOW_MENU             2
-#define NS_STYLE_WINDOW_SHADOW_TOOLTIP          3
-#define NS_STYLE_WINDOW_SHADOW_SHEET            4
 
 /**
  * Transparency modes
  */
 
 enum nsTransparencyMode {
   eTransparencyOpaque = 0,  // Fully opaque
   eTransparencyTransparent, // Parts of the window may be transparent