add Tickmarks to aura overlay scrollbar

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

Index: third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.h b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.h
index d746291a522d339095ccd0da569927ea065f8bfd..9b3088bddeaf61fae5bd8df8cdef0cc5ecb6878d 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.h
@@ -66,6 +66,9 @@ class PLATFORM_EXPORT ScrollbarThemeOverlay : public ScrollbarTheme {
                             bool painting = false) override;
   IntRect trackRect(const ScrollbarThemeClient&,
                     bool painting = false) override;
+  void paintTickmarks(GraphicsContext&,

[bokan, 2016/11/04 19:46:25]

Android uses this ScrollbarTheme, how do they draw tickmarks in Android?
Presumably there's some special path?

+                      const Scrollbar&,
+                      const IntRect&) override;
   int thumbThickness(const ScrollbarThemeClient&) override;
   int thumbThickness() { return m_thumbThickness; }