Paint state transition for overlay 9 patch scrollbars

ui/native_theme/native_theme_base.h

Index: ui/native_theme/native_theme_base.h
diff --git a/ui/native_theme/native_theme_base.h b/ui/native_theme/native_theme_base.h
index d9c2fbadb3ba90bf8edd1cfafe916e5ac038320c..e19a933cbad0bf7b7cb8532c2a4fd91916140735 100644
--- a/ui/native_theme/native_theme_base.h
+++ b/ui/native_theme/native_theme_base.h
@@ -33,6 +33,13 @@ class NATIVE_THEME_EXPORT NativeThemeBase : public NativeTheme {
                      const gfx::Rect& rect,
                      const ExtraParams& extra) const OVERRIDE;
 
+  virtual void PaintStateTransition(SkCanvas* canvas,
+                                    Part part,
+                                    State startState,
+                                    State endState,
+                                    double progress,
+                                    const gfx::Rect& rect) const OVERRIDE;
+
  protected:
   NativeThemeBase();
   virtual ~NativeThemeBase();
@@ -130,6 +137,13 @@ class NATIVE_THEME_EXPORT NativeThemeBase : public NativeTheme {
       const gfx::Rect& rect,
       const ProgressBarExtraParams& progress_bar) const;
 
+  virtual void PaintScrollbarThumbStateTransition(
+      SkCanvas* canvas,
+      State startState,
+      State endState,
+      double progress,
+      const gfx::Rect& rect) const {}
+
   void set_scrollbar_button_length(unsigned int length) {
     scrollbar_button_length_ = length;
   }