Draw infobar arrow border with width of 1px on any scale factor.

chrome/browser/ui/views/infobars/infobar_background.h

 // Copyright (c) 2011 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 CHROME_BROWSER_UI_VIEWS_INFOBARS_INFOBAR_BACKGROUND_H_
 #define CHROME_BROWSER_UI_VIEWS_INFOBARS_INFOBAR_BACKGROUND_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "components/infobars/core/infobar_delegate.h"
 #include "ui/views/background.h"
 
 class InfoBarBackground : public views::Background {
  public:
   explicit InfoBarBackground(infobars::InfoBarDelegate::Type infobar_type);
   ~InfoBarBackground() override;
 
-  void set_separator_color(SkColor color) { separator_color_ = color; }
-
  private:
   // views::Background:
   void Paint(gfx::Canvas* canvas, views::View* view) const override;
 
-  SkColor separator_color_;
+  void PaintMd(gfx::Canvas* canvas, views::View* view) const;
+
   SkColor top_color_;
   SkColor bottom_color_;
 
   DISALLOW_COPY_AND_ASSIGN(InfoBarBackground);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_INFOBARS_INFOBAR_BACKGROUND_H_