Aura overlay scrollbars adjust color for dark backgrounds

ui/native_theme/native_theme_aura.h

Index: ui/native_theme/native_theme_aura.h
diff --git a/ui/native_theme/native_theme_aura.h b/ui/native_theme/native_theme_aura.h
index 596552fb16e4a8763779059a8b5407a9b869fd54..32164f65e6b975f28cd43433e0ce0a3efdfce319 100644
--- a/ui/native_theme/native_theme_aura.h
+++ b/ui/native_theme/native_theme_aura.h
@@ -42,17 +42,20 @@ class NATIVE_THEME_EXPORT NativeThemeAura : public NativeThemeBase {
   void PaintScrollbarThumb(SkCanvas* canvas,
                            Part part,
                            State state,
-                           const gfx::Rect& rect) const override;
+                           const gfx::Rect& rect,
+                           ScrollbarOverlayColorTheme theme) const override;
   void PaintScrollbarCorner(SkCanvas* canvas,
                             State state,
                             const gfx::Rect& rect) const override;
 
-  void PaintScrollbarThumbStateTransition(SkCanvas* canvas,
-                                          Part part,
-                                          State startState,
-                                          State endState,
-                                          double progress,
-                                          const gfx::Rect& rect) const override;
+  void PaintScrollbarThumbStateTransition(

[bokan, 2016/10/27 15:14:49]

The only actual caller of this method is PaintScrollbarThumb. Remove this method
and put its implementation directly in PaintScrollbarThumb. Also remove
NativeThemeBase::PaintScrollbarThumbTransition which calls here but has no
callers.

+      SkCanvas* canvas,
+      Part part,
+      State startState,
+      State endState,
+      double progress,
+      const gfx::Rect& rect,
+      ScrollbarOverlayColorTheme theme) const override;
   gfx::Size GetPartSize(Part part,
                         State state,
                         const ExtraParams& extra) const override;