Paint state transition for overlay 9 patch scrollbars

ui/native_theme/native_theme_aura.h

Index: ui/native_theme/native_theme_aura.h
diff --git a/ui/native_theme/native_theme_aura.h b/ui/native_theme/native_theme_aura.h
index 65c70ff324a071840d9308ddc3aecff65d41ddac..b63556c02849b88f61e7499e6e4e887c674346bd 100644
--- a/ui/native_theme/native_theme_aura.h
+++ b/ui/native_theme/native_theme_aura.h
@@ -52,6 +52,13 @@ class NATIVE_THEME_EXPORT NativeThemeAura : public FallbackTheme {
                                     State state,
                                     const gfx::Rect& rect) const OVERRIDE;
 
+  virtual void PaintScrollbarThumbStateTransition(SkCanvas* canvas,
+                                                  State startState,
+                                                  State endState,
+                                                  double progress,
+                                                  const gfx::Rect& rect) const
+      OVERRIDE;
+
   // Returns the NineImagePainter used to paint the specified state, creating if
   // necessary. If no image is provided for the specified state the normal state
   // images are used.
@@ -105,6 +112,13 @@ class NATIVE_THEME_EXPORT NativeThemeAura : public FallbackTheme {
                         const gfx::Rect& rect,
                         State state) const;
 
+  void PaintDualPainterTransition(DualPainter* dual_painter,
+                                  SkCanvas* sk_canvas,
+                                  const gfx::Rect& rect,
+                                  State startState,
+                                  State endState,
+                                  double progress) const;
+
   mutable scoped_ptr<DualPainter> scrollbar_overlay_thumb_painter_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeThemeAura);