Native themes: Add separator color

ui/views/controls/separator.h

Index: ui/views/controls/separator.h
diff --git a/ui/views/controls/separator.h b/ui/views/controls/separator.h
index 45e23b3a7daaca6675d0bb425964f0b0b07e3a52..d4689fe209748b9241bebf63b616d9227a4ccf91 100644
--- a/ui/views/controls/separator.h
+++ b/ui/views/controls/separator.h
@@ -40,11 +40,15 @@ class VIEWS_EXPORT Separator : public View {
   gfx::Size GetPreferredSize() const override;
   void GetAccessibleNodeData(ui::AXNodeData* node_data) override;
   void OnPaint(gfx::Canvas* canvas) override;
+  void OnNativeThemeChanged(const ui::NativeTheme* theme) override;
   const char* GetClassName() const override;
 
  private:
+  void SetColorFromNativeTheme();
+
   const Orientation orientation_;
   SkColor color_;
+  bool color_overridden_;
   int size_;
 
   DISALLOW_COPY_AND_ASSIGN(Separator);