[MD] Don't use new OTR native-theming when using a custom browser theme.

ui/views/widget/widget.h

Index: ui/views/widget/widget.h
diff --git a/ui/views/widget/widget.h b/ui/views/widget/widget.h
index 54c6d29c959ad5f4389247bc84fe1f0236c5979b..11778fd7fa08b36c781bf0ac093c5de0482ca1c7 100644
--- a/ui/views/widget/widget.h
+++ b/ui/views/widget/widget.h
@@ -241,8 +241,6 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
     // When set, this value is used as the Widget's NativeWidget implementation.
     // The Widget will not construct a default one. Default is NULL.
     NativeWidget* native_widget;
-    // If provided, sets the native theme for this widget.
-    ui::NativeTheme* native_theme;
     // Aura-only. Provides a DesktopWindowTreeHost implementation to use instead
     // of the default one.
     // TODO(beng): Figure out if there's a better way to expose this, e.g. get
@@ -564,7 +562,7 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
     return const_cast<ui::NativeTheme*>(
         const_cast<const Widget*>(this)->GetNativeTheme());
   }
-  const ui::NativeTheme* GetNativeTheme() const;
+  virtual const ui::NativeTheme* GetNativeTheme() const;
 
   // Returns the FocusManager for this widget.
   // Note that all widgets in a widget hierarchy share the same focus manager.
@@ -865,10 +863,6 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
 
   internal::NativeWidgetPrivate* native_widget_;
 
-  // If non-null, the native theme for this widget. Otherwise the native theme
-  // comes from |native_widget_|.
-  ui::NativeTheme* native_theme_;
-
   base::ObserverList<WidgetObserver> observers_;
 
   base::ObserverList<WidgetRemovalsObserver> removals_observers_;