add Tickmarks to aura overlay scrollbar

third_party/WebKit/Source/platform/scroll/ScrollbarTheme.h

Index: third_party/WebKit/Source/platform/scroll/ScrollbarTheme.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollbarTheme.h b/third_party/WebKit/Source/platform/scroll/ScrollbarTheme.h
index 1d7840e92cd57ac82fa438c6a7e81b007da56c24..dfc7618b02d8f26b1dfc5b4ae6f687e1f27583d4 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollbarTheme.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollbarTheme.h
@@ -88,7 +88,7 @@ class PLATFORM_EXPORT ScrollbarTheme {
                                  const IntRect& cornerRect);
   virtual void paintTickmarks(GraphicsContext&,
                               const Scrollbar&,
-                              const IntRect&) {}
+                              const IntRect&);
 
   virtual bool shouldCenterOnThumb(const ScrollbarThemeClient&,
                                    const PlatformMouseEvent&);
@@ -178,6 +178,10 @@ class PLATFORM_EXPORT ScrollbarTheme {
  protected:
   static DisplayItem::Type buttonPartToDisplayItemType(ScrollbarPart);
   static DisplayItem::Type trackPiecePartToDisplayItemType(ScrollbarPart);
+  static void paintTickmarksWithBorderWidth(GraphicsContext&,
+                                            const Scrollbar&,
+                                            const IntRect&,
+                                            const int);
 
  private:
   static ScrollbarTheme&