diff --git a/widget/gtk/gtk3drawing.c b/widget/gtk/gtk3drawing.c
index 7ffabf8bd128..b053f5532676 100644
--- a/widget/gtk/gtk3drawing.c
+++ b/widget/gtk/gtk3drawing.c
@@ -1133,6 +1133,7 @@ static gint
 moz_gtk_scrollbar_trough_paint(GtkThemeWidgetType widget,
                                cairo_t *cr, GdkRectangle* rect,
                                GtkWidgetState* state,
+                               GtkScrollbarTrackFlags flags,
                                GtkTextDirection direction)
 {
     GtkStyleContext* style;
@@ -1147,6 +1148,11 @@ moz_gtk_scrollbar_trough_paint(GtkThemeWidgetType widget,
 
     gtk_widget_set_direction(GTK_WIDGET(scrollbar), direction);
     
+    if (flags & MOZ_GTK_TRACK_OPAQUE) {
+        style = gtk_widget_get_style_context(GTK_WIDGET(gProtoWindow));
+        gtk_render_background(style, cr, rect->x, rect->y, rect->width, rect->height);
+    }
+
     style = gtk_widget_get_style_context(GTK_WIDGET(scrollbar));
     gtk_style_context_save(style);
     gtk_style_context_add_class(style, GTK_STYLE_CLASS_TROUGH);
@@ -3104,7 +3110,9 @@ moz_gtk_widget_paint(GtkThemeWidgetType widget, cairo_t *cr,
     case MOZ_GTK_SCROLLBAR_TRACK_HORIZONTAL:
     case MOZ_GTK_SCROLLBAR_TRACK_VERTICAL:
         return moz_gtk_scrollbar_trough_paint(widget, cr, rect,
-                                              state, direction);
+                                              state,
+                                              (GtkScrollbarTrackFlags) flags,
+                                              direction);
         break;
     case MOZ_GTK_SCROLLBAR_THUMB_HORIZONTAL:
     case MOZ_GTK_SCROLLBAR_THUMB_VERTICAL:
diff --git a/widget/gtk/gtkdrawing.h b/widget/gtk/gtkdrawing.h
index e83bf467f712..da30e1f5eb33 100644
--- a/widget/gtk/gtkdrawing.h
+++ b/widget/gtk/gtkdrawing.h
@@ -51,6 +51,10 @@ typedef enum {
   MOZ_GTK_STEPPER_VERTICAL    = 1 << 2
 } GtkScrollbarButtonFlags;
 
+typedef enum {
+  MOZ_GTK_TRACK_OPAQUE        = 1 << 0
+} GtkScrollbarTrackFlags;
+
 /** flags for tab state **/
 typedef enum {
   /* first eight bits are used to pass a margin */
diff --git a/widget/gtk/nsNativeThemeGTK.cpp b/widget/gtk/nsNativeThemeGTK.cpp
index 1b4a50387037..c5d335c169dd 100644
--- a/widget/gtk/nsNativeThemeGTK.cpp
+++ b/widget/gtk/nsNativeThemeGTK.cpp
@@ -412,9 +412,17 @@ nsNativeThemeGTK::GetGtkWidgetAndState(uint8_t aWidgetType, nsIFrame* aFrame,
     break;
   case NS_THEME_SCROLLBAR_TRACK_VERTICAL:
     aGtkWidgetType = MOZ_GTK_SCROLLBAR_TRACK_VERTICAL;
+    if (GetWidgetTransparency(aFrame, aWidgetType) == eOpaque)
+        *aWidgetFlags = MOZ_GTK_TRACK_OPAQUE;
+    else
+        *aWidgetFlags = 0;
     break;
   case NS_THEME_SCROLLBAR_TRACK_HORIZONTAL:
     aGtkWidgetType = MOZ_GTK_SCROLLBAR_TRACK_HORIZONTAL;
+    if (GetWidgetTransparency(aFrame, aWidgetType) == eOpaque)
+        *aWidgetFlags = MOZ_GTK_TRACK_OPAQUE;
+    else
+        *aWidgetFlags = 0;
     break;
   case NS_THEME_SCROLLBAR_THUMB_VERTICAL:
     aGtkWidgetType = MOZ_GTK_SCROLLBAR_THUMB_VERTICAL;
@@ -1807,8 +1815,6 @@ nsNativeThemeGTK::GetWidgetTransparency(nsIFrame* aFrame, uint8_t aWidgetType)
   switch (aWidgetType) {
   // These widgets always draw a default background.
 #if (MOZ_WIDGET_GTK == 2)
-  case NS_THEME_SCROLLBAR_TRACK_VERTICAL:
-  case NS_THEME_SCROLLBAR_TRACK_HORIZONTAL:
   case NS_THEME_TOOLBAR:
   case NS_THEME_MENUBAR:
 #endif
@@ -1816,6 +1822,17 @@ nsNativeThemeGTK::GetWidgetTransparency(nsIFrame* aFrame, uint8_t aWidgetType)
   case NS_THEME_WINDOW:
   case NS_THEME_DIALOG:
     return eOpaque;
+  case NS_THEME_SCROLLBAR_TRACK_VERTICAL:
+  case NS_THEME_SCROLLBAR_TRACK_HORIZONTAL:
+#if (MOZ_WIDGET_GTK == 3)
+    // Make scrollbar tracks opaque on the window's scroll frame to prevent
+    // leaf layers from overlapping. See bug 1179780.
+    if (!(CheckBooleanAttr(aFrame, nsGkAtoms::root_) &&
+          aFrame->PresContext()->IsRootContentDocument() &&
+          IsFrameContentNodeInNamespace(aFrame, kNameSpaceID_XUL)))
+      return eTransparent;
+#endif
+    return eOpaque;
   // Tooltips use gtk_paint_flat_box() on Gtk2
   // but are shaped on Gtk3
   case NS_THEME_TOOLTIP: