--- a/layout/style/ServoBindingList.h
+++ b/layout/style/ServoBindingList.h
@@ -42,18 +42,18 @@ SERVO_BINDING_FUNC(Servo_StyleSheet_Clon
 SERVO_BINDING_FUNC(Servo_StyleSheet_SizeOfIncludingThis, size_t,
                    mozilla::MallocSizeOf malloc_size_of,
                    RawServoStyleSheetContentsBorrowed sheet)
 SERVO_BINDING_FUNC(Servo_StyleSet_Init, RawServoStyleSetOwned, RawGeckoPresContextOwned pres_context)
 SERVO_BINDING_FUNC(Servo_StyleSet_Clear, void,
                    RawServoStyleSetBorrowed set)
 SERVO_BINDING_FUNC(Servo_StyleSet_RebuildData, void,
                    RawServoStyleSetBorrowed set)
-SERVO_BINDING_FUNC(Servo_StyleSet_MediumFeaturesChanged, bool,
-                   RawServoStyleSetBorrowed set)
+SERVO_BINDING_FUNC(Servo_StyleSet_MediumFeaturesChanged, nsRestyleHint,
+                   RawServoStyleSetBorrowed set, bool viewport_changed)
 SERVO_BINDING_FUNC(Servo_StyleSet_Drop, void, RawServoStyleSetOwned set)
 SERVO_BINDING_FUNC(Servo_StyleSet_CompatModeChanged, void,
                    RawServoStyleSetBorrowed raw_data)
 SERVO_BINDING_FUNC(Servo_StyleSet_AppendStyleSheet, void,
                    RawServoStyleSetBorrowed set,
                    const mozilla::ServoStyleSheet* gecko_sheet)
 SERVO_BINDING_FUNC(Servo_StyleSet_PrependStyleSheet, void,
                    RawServoStyleSetBorrowed set,

--- a/layout/style/ServoStyleSet.cpp
+++ b/layout/style/ServoStyleSet.cpp
@@ -111,27 +111,17 @@ ServoStyleSet::InvalidateStyleForCSSRule
 {
   MOZ_ASSERT(StylistNeedsUpdate());
   mPresContext->RestyleManager()->AsServo()->PostRestyleEventForCSSRuleChanges();
 }
 
 nsRestyleHint
 ServoStyleSet::MediumFeaturesChanged(bool aViewportChanged) const
 {
-  if (Servo_StyleSet_MediumFeaturesChanged(mRawSet.get())) {
-    return eRestyle_Subtree;
-  }
-  if (aViewportChanged) {
-    // Rebuild all style data without rerunning selector matching.
-    //
-    // FIXME(emilio, bug 1328652): We don't set mUsesViewportUnits in stylo yet,
-    // so assume the worst.
-    return eRestyle_ForceDescendants;
-  }
-  return nsRestyleHint(0);
+  return Servo_StyleSet_MediumFeaturesChanged(mRawSet.get(), aViewportChanged);
 }
 
 size_t
 ServoStyleSet::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
 {
   size_t n = aMallocSizeOf(this);
 
   if (mStyleRuleMap) {