views::Separator cleanup.

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 d4689fe209748b9241bebf63b616d9227a4ccf91..d231d3a22308e1794118475543058caa96a9769a 100644
--- a/ui/views/controls/separator.h
+++ b/ui/views/controls/separator.h
@@ -8,6 +8,7 @@
 #include <string>
 
 #include "base/macros.h"
+#include "base/optional.h"
 #include "ui/views/view.h"
 
 namespace views {
@@ -18,38 +19,39 @@ namespace views {
 class VIEWS_EXPORT Separator : public View {
  public:
   enum Orientation {
+    // The separator is a horizontal line that distinguishes vertically stacked
+    // elements.
     HORIZONTAL,
-    VERTICAL
+    // The separator is a vertical line that distinguishes a row of elements.
+    VERTICAL,
   };
 
   // The separator's class name.
   static const char kViewClassName[];
 
+  // The separator's thickness in dip.
+  static const int kThickness;
+
   explicit Separator(Orientation orientation);
   ~Separator() override;
 
-  SkColor color() const { return color_; }
   void SetColor(SkColor color);
 
-  int size() const { return size_; }
-  // Preferred size of one axis: height for horizontal separator
-  // and width for vertical separator
-  void SetPreferredSize(int size);
+  // Preferred length: width for horizontal separator and height for vertical
+  // separator.
+  void SetPreferredLength(int length);
 
   // Overridden from 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_;
+  base::Optional<SkColor> overridden_color_;
+  // The length to request in GetPreferredSize().
+  int length_ = 1;
 
   DISALLOW_COPY_AND_ASSIGN(Separator);
 };