Make SysColorChangeListener Windows-only instead of having an empty shell.

ui/gfx/color_utils.h

Index: ui/gfx/color_utils.h
diff --git a/ui/gfx/color_utils.h b/ui/gfx/color_utils.h
index 9153688ad9b908563915ff2ec6785d2d98af0c39..f49054520f4163f5de055bcccd4fdda866bd8e0a 100644
--- a/ui/gfx/color_utils.h
+++ b/ui/gfx/color_utils.h
@@ -103,6 +103,11 @@ GFX_EXPORT SkColor InvertColor(SkColor color);
 // Gets a Windows system color as a SkColor
 GFX_EXPORT SkColor GetSysSkColor(int which);
 
+// Returns true only if Chrome should use an inverted color scheme - which is
+// only true if the system has high-contrast mode enabled and and is using a
+// light-on-dark color scheme.
+GFX_EXPORT bool IsInvertedColorScheme();
+
 }  // namespace color_utils
 
 #endif  // UI_GFX_COLOR_UTILS_H_