diff --git a/widget/gtk/gtk3drawing.cpp b/widget/gtk/gtk3drawing.cpp
index 1eb37c878cee..e079d46f1a84 100644
--- a/widget/gtk/gtk3drawing.cpp
+++ b/widget/gtk/gtk3drawing.cpp
@@ -39,9 +39,6 @@ static gint
 moz_gtk_menu_item_paint(WidgetNodeType widget, cairo_t *cr, GdkRectangle* rect,
                         GtkWidgetState* state, GtkTextDirection direction);
 
-static GtkBorder
-GetMarginBorderPadding(GtkStyleContext* aStyle);
-
 // GetStateFlagsFromGtkWidgetState() can be safely used for the specific
 // GtkWidgets that set both prelight and active flags.  For other widgets,
 // either the GtkStateFlags or Gecko's GtkWidgetState need to be carefully
@@ -654,37 +651,12 @@ moz_gtk_draw_styled_frame(GtkStyleContext* style, cairo_t *cr,
 
 static gint
 moz_gtk_scrollbar_trough_paint(WidgetNodeType widget,
-                               cairo_t *cr, const GdkRectangle* aRect,
+                               cairo_t *cr, const GdkRectangle* rect,
                                GtkWidgetState* state,
                                GtkTextDirection direction)
 {
-    GdkRectangle rect = *aRect;
-    GtkStyleContext* style;
-
-    if (gtk_get_minor_version() >= 20) {
-        WidgetNodeType thumb = widget == MOZ_GTK_SCROLLBAR_TROUGH_VERTICAL ?
-            MOZ_GTK_SCROLLBAR_THUMB_VERTICAL :
-            MOZ_GTK_SCROLLBAR_THUMB_HORIZONTAL;
-        MozGtkSize thumbSize = GetMinMarginBox(thumb);
-        style = ClaimStyleContext(widget, direction);
-        MozGtkSize trackSize = GetMinContentBox(style);
-        trackSize.Include(thumbSize);
-        trackSize += GetMarginBorderPadding(style);
-        // Gecko's trough |aRect| fills available breadth, but GTK's trough is
-        // centered in the contents_gadget.  The centering here round left
-        // and up, like gtk_box_gadget_allocate_child().
-        if (widget == MOZ_GTK_SCROLLBAR_TROUGH_VERTICAL) {
-            rect.x += (rect.width - trackSize.width)/2;
-            rect.width = trackSize.width;
-        } else {
-            rect.y += (rect.height - trackSize.height)/2;
-            rect.height = trackSize.height;
-        }
-    } else {
-        style = ClaimStyleContext(widget, direction);
-    }
-
-    moz_gtk_draw_styled_frame(style, cr, &rect, state->focused);
+    GtkStyleContext* style = ClaimStyleContext(widget, direction);
+    moz_gtk_draw_styled_frame(style, cr, rect, state->focused);
     ReleaseStyleContext(style);
 
     return MOZ_GTK_SUCCESS;
diff --git a/widget/gtk/gtkdrawing.h b/widget/gtk/gtkdrawing.h
index 9753174443a2..521ed05e09c7 100644
--- a/widget/gtk/gtkdrawing.h
+++ b/widget/gtk/gtkdrawing.h
@@ -46,21 +46,11 @@ struct MozGtkSize {
   gint width;
   gint height;
 
-  MozGtkSize& operator+=(const GtkBorder& aBorder)
-  {
-    width += aBorder.left + aBorder.right;
-    height += aBorder.top + aBorder.bottom;
-    return *this;
-  }
   MozGtkSize operator+(const GtkBorder& aBorder) const
   {
-    MozGtkSize result = *this;
-    return result += aBorder;
-  }
-  void Include(MozGtkSize aOther)
-  {
-    width = std::max(width, aOther.width);
-    height = std::max(height, aOther.height);
+    gint resultWidth = width + aBorder.left + aBorder.right;
+    gint resultHeight = height + aBorder.top + aBorder.bottom;
+    return {resultWidth, resultHeight};
   }
   void Rotate()
   {