Enable hidpi on Linux, refactor a bit on Windows to share

ui/views/controls/menu/menu_separator_win.cc

Index: ui/views/controls/menu/menu_separator_win.cc
diff --git a/ui/views/controls/menu/menu_separator_win.cc b/ui/views/controls/menu/menu_separator_win.cc
index 98a70baa6711c8573d18b8e5df5daaab45d50602..7265c169c9c3b7ea47315a675bd94ea503541a81 100644
--- a/ui/views/controls/menu/menu_separator_win.cc
+++ b/ui/views/controls/menu/menu_separator_win.cc
@@ -9,8 +9,8 @@
 #include <Vssym32.h>
 
 #include "ui/gfx/canvas.h"
+#include "ui/gfx/dpi.h"
 #include "ui/gfx/rect.h"
-#include "ui/gfx/win/dpi.h"
 #include "ui/native_theme/native_theme.h"
 #include "ui/native_theme/native_theme_aura.h"
 #include "ui/views/controls/menu/menu_config.h"
@@ -46,7 +46,7 @@ void MenuSeparator::OnPaint(gfx::Canvas* canvas) {
   // Hack to get the separator to display correctly on Windows where we may
   // have fractional scales. We move the separator 1 pixel down to ensure that
   // it falls within the clipping rect which is scaled up.
-  float device_scale = gfx::win::GetDeviceScaleFactor();
+  float device_scale = gfx::GetDeviceScaleFactor();
   bool is_fractional_scale =
       (device_scale - static_cast<int>(device_scale) != 0);
   if (is_fractional_scale && separator_bounds.y() == 0)