diff -up chromium-61.0.3163.79/chrome/browser/ui/libgtkui/gtk_ui.cc.gtk2fix chromium-61.0.3163.79/chrome/browser/ui/libgtkui/gtk_ui.cc

--- chromium-61.0.3163.79/chrome/browser/ui/libgtkui/gtk_ui.cc.gtk2fix	2017-09-07 15:40:40.904966476 -0400

+++ chromium-61.0.3163.79/chrome/browser/ui/libgtkui/gtk_ui.cc	2017-09-07 15:42:23.829987464 -0400

@@ -1052,11 +1052,19 @@ float GtkUi::GetRawDeviceScaleFactor() {

   if (display::Display::HasForceDeviceScaleFactor())

     return display::Display::GetForcedDeviceScaleFactor();

+#if GTK_MAJOR_VERSION == 2

+  GtkSettings* gtk_settings = gtk_settings_get_default();

+  gint gtk_dpi = -1;

+  g_object_get(gtk_settings, "gtk-xft-dpi", &gtk_dpi, nullptr);

+  const float scale_factor = gtk_dpi / (1024 * kDefaultDPI);

+#else

   GdkScreen* screen = gdk_screen_get_default();

   gint scale = gtk_widget_get_scale_factor(fake_window_);

   gdouble resolution = gdk_screen_get_resolution(screen);

   const float scale_factor =

       resolution <= 0 ? scale : resolution * scale / kDefaultDPI;

+#endif

+

   // Blacklist scaling factors <120% (crbug.com/484400) and round

   // to 1 decimal to prevent rendering problems (crbug.com/485183).

   return scale_factor < 1.2f ? 1.0f : roundf(scale_factor * 10) / 10;