Use nine-patch resource for drawing Aura overlay scrollbar thumb.

ui/native_theme/native_theme_win.cc

Index: ui/native_theme/native_theme_win.cc
diff --git a/ui/native_theme/native_theme_win.cc b/ui/native_theme/native_theme_win.cc
index e0d92f10cee0223caa9fafe7d2edbca9a083158c..72888839039e9c23de5dc00c3ed97d01ce30a1e7 100644
--- a/ui/native_theme/native_theme_win.cc
+++ b/ui/native_theme/native_theme_win.cc
@@ -660,6 +660,22 @@ SkColor NativeThemeWin::GetSystemColor(ColorId color_id) const {
   return GetAuraColor(color_id, this);
 }
 
+bool NativeThemeWin::SupportsNinePatch(Part part) const {
+  // The only nine-patch resources currently supported (overlay scrollbar) are
+  // paitned by NativeThemeAura on Windows.

[sadrul, 2017/03/01 16:30:27]

*painted

[bokan, 2017/03/01 17:02:31]

Done.

+  return false;
+}
+
+gfx::Size NativeThemeWin::GetNinePatchCanvasSize(Part part) const {
+  NOTREACHED() << "NativeThemeWin doesn't support nine-patch resources.";
+  return gfx::Size();
+}
+
+gfx::Rect NativeThemeWin::GetNinePatchAperture(Part part) const {
+  NOTREACHED() << "NativeThemeWin doesn't support nine-patch resources.";
+  return gfx::Rect();
+}
+
 void NativeThemeWin::PaintIndirect(cc::PaintCanvas* destination_canvas,
                                    Part part,
                                    State state,