Aura overlay scrollbars adjust color for dark backgrounds

ui/native_theme/native_theme.h

Index: ui/native_theme/native_theme.h
diff --git a/ui/native_theme/native_theme.h b/ui/native_theme/native_theme.h
index 664aa50e4ee938f6bd30422bae9cf4a66220b6de..4821ae18e3026da9381b55b21f3dabf05b63e79b 100644
--- a/ui/native_theme/native_theme.h
+++ b/ui/native_theme/native_theme.h
@@ -175,6 +175,12 @@ class NATIVE_THEME_EXPORT NativeTheme {
     bool is_hovering;
   };
 
+  enum ScrollbarOverlayColorTheme {
+    ScrollbarOverlayColorThemeDefault,
+    ScrollbarOverlayColorThemeDark,
+    ScrollbarOverlayColorThemeLight
+  };
+
   struct SliderExtraParams {
     bool vertical;
     bool in_drag;
@@ -211,6 +217,7 @@ class NATIVE_THEME_EXPORT NativeTheme {
     ScrollbarArrowExtraParams scrollbar_arrow;
     ScrollbarTrackExtraParams scrollbar_track;
     ScrollbarThumbExtraParams scrollbar_thumb;
+    ScrollbarOverlayColorTheme scrollbar_theme;

[bokan, 2016/10/21 16:57:14]

This doesn't belong here, this is a union (if you're coming from Java you
probably won't have seen it, http://en.cppreference.com/w/cpp/language/union).
It should be inside ScrollbarThumbExtraParams.

     SliderExtraParams slider;
     TextFieldExtraParams text_field;
     TrackbarExtraParams trackbar;
@@ -235,7 +242,8 @@ class NATIVE_THEME_EXPORT NativeTheme {
                                     State startState,
                                     State endState,
                                     double progress,
-                                    const gfx::Rect& rect) const { }
+                                    const gfx::Rect& rect,
+                                    ScrollbarOverlayColorTheme theme) const {}
 
   // Supports theme specific colors.
   void SetScrollbarColors(unsigned inactive_color,