Change Aura overlay scrollbars from solid color to painted scrollbars.

ui/native_theme/native_theme_base.h

Index: ui/native_theme/native_theme_base.h
diff --git a/ui/native_theme/native_theme_base.h b/ui/native_theme/native_theme_base.h
index 3a8ddde23d1244ffdd37e2d09b88a4467b2660d5..a2782ae105b210c3ee381a28434c6971a28d8101 100644
--- a/ui/native_theme/native_theme_base.h
+++ b/ui/native_theme/native_theme_base.h
@@ -169,6 +169,8 @@ class NATIVE_THEME_EXPORT NativeThemeBase : public NativeTheme {
   // Returns the color used to draw the arrow.
   SkColor GetArrowColor(State state) const;
 
+  unsigned int scrollbar_width_;

[Peter Kasting, 2016/10/17 19:10:25]

Nit: unsigned int is banned.  I know you are just moving this code up, but try
to change this to int.

[bokan, 2016/10/17 23:21:04]

Done. (also for button length below)

+
  private:
   friend class NativeThemeAuraTest;
 
@@ -201,8 +203,6 @@ class NATIVE_THEME_EXPORT NativeThemeBase : public NativeTheme {
       const gfx::Rect& rect,
       const SkScalar borderRadius) const;
 
-  unsigned int scrollbar_width_;
-
   // The length of the arrow buttons, 0 means no buttons are drawn.
   unsigned int scrollbar_button_length_;