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

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

Index: chrome/browser/ui/views/infobars/infobar_background.h
diff --git a/chrome/browser/ui/views/infobars/infobar_background.h b/chrome/browser/ui/views/infobars/infobar_background.h
index 631c3df78d657431975fb4e76d6c1f7a62208285..1cb689b07dd92e7e6da64357844b8962eb8f16ee 100644
--- a/chrome/browser/ui/views/infobars/infobar_background.h
+++ b/chrome/browser/ui/views/infobars/infobar_background.h
@@ -15,13 +15,12 @@ class InfoBarBackground : public views::Background {
   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_;