Revert of Clean up some NativeTheme code.

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 b823568421782e289434a9da3d58bde330b0e9da..e2fbfc4e741f42ac764795f448c36849b3579edd 100644
--- a/ui/native_theme/native_theme_aura.h
+++ b/ui/native_theme/native_theme_aura.h
@@ -14,10 +14,9 @@
 class NATIVE_THEME_EXPORT NativeThemeAura : public NativeThemeBase {
  public:
   static NativeThemeAura* instance();
-  static NativeThemeAura* web_instance();
 
  protected:
-  explicit NativeThemeAura(bool use_overlay_scrollbars);
+  NativeThemeAura();
   ~NativeThemeAura() override;
 
   // Overridden from NativeThemeBase:
@@ -53,8 +52,6 @@
                         const ExtraParams& extra) const override;
 
  private:
-  bool use_overlay_scrollbars_;
-
   DISALLOW_COPY_AND_ASSIGN(NativeThemeAura);
 };