MacViews: Style BUTTON_STYLE buttons using the "modern" UI

ui/views/style/mac/dialog_button_border_mac.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_VIEWS_STYLE_MAC_DIALOG_BUTTON_BORDER_MAC_H_
 #define UI_VIEWS_STYLE_MAC_DIALOG_BUTTON_BORDER_MAC_H_
 
 #include "base/macros.h"
 #include "ui/views/controls/button/label_button_border.h"
 #include "ui/views/views_export.h"
 
 namespace views {
 
+class LabelButton;
+
 // Skia port of the default button style used for dialogs on Chrome Mac.
 // Originally provided by ConstrainedWindowButton, which used Quartz-backed
 // Cocoa drawing routines.
 class VIEWS_EXPORT DialogButtonBorderMac : public LabelButtonBorder {
  public:
   DialogButtonBorderMac();
   ~DialogButtonBorderMac() override;
 
+  // Whether the given |button| should get a highlighted background.
+  static bool ShouldRenderDefault(const LabelButton& button);
+
   // views::Border:
   void Paint(const View& view, gfx::Canvas* canvas) override;
   gfx::Size GetMinimumSize() const override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DialogButtonBorderMac);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_STYLE_MAC_DIALOG_BUTTON_BORDER_MAC_H_