--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -6615,16 +6615,23 @@ nsWindow::ClearCachedResources()
     for (GList* list = children; list; list = list->next) {
         nsWindow* window = get_window_for_gdk_window(GDK_WINDOW(list->data));
         if (window) {
             window->ClearCachedResources();
         }
     }
 }
 
+nsresult
+nsWindow::SetNonClientMargins(LayoutDeviceIntMargin &aMargins)
+{
+  SetDrawsInTitlebar(aMargins.top == 0);
+  return NS_OK;
+}
+
 void
 nsWindow::SetDrawsInTitlebar(bool aState)
 {
   if (!mIsCSDAvailable || aState == mIsCSDEnabled)
       return;
 
   if (mShell) {
       gint wmd = aState ? GDK_DECOR_BORDER : ConvertBorderStyles(mBorderStyle);

--- a/widget/gtk/nsWindow.h
+++ b/widget/gtk/nsWindow.h
@@ -346,16 +346,17 @@ public:
                                                 nsIObserver* aObserver) override;
 #endif
 
 #ifdef MOZ_X11
     Display* XDisplay() { return mXDisplay; }
 #endif
     virtual void GetCompositorWidgetInitData(mozilla::widget::CompositorWidgetInitData* aInitData) override;
 
+    virtual nsresult SetNonClientMargins(LayoutDeviceIntMargin& aMargins) override;
     void SetDrawsInTitlebar(bool aState) override;
 
     // HiDPI scale conversion
     gint GdkScaleFactor();
 
     // To GDK
     gint DevicePixelsToGdkCoordRoundUp(int pixels);
     gint DevicePixelsToGdkCoordRoundDown(int pixels);