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

ui/views/controls/menu/menu_separator_win.cc

 // Copyright (c) 2012 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.
 
 #include "ui/views/controls/menu/menu_separator.h"
 
 #include <windows.h>
 #include <uxtheme.h>
 #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"
 #include "ui/views/controls/menu/menu_item_view.h"
 
 namespace views {
 
 void MenuSeparator::OnPaint(gfx::Canvas* canvas) {
   const MenuConfig& config = parent_menu_item_->GetMenuConfig();
 
@@ skipping 15 matching lines @@
         ui::NativeTheme::kNormal, gutter_bounds, extra);
     separator_bounds.set_x(gutter_bounds.x() + config.gutter_width);
   }
 
   ui::NativeTheme::ExtraParams extra;
   extra.menu_separator.has_gutter = config.render_gutter;
 
   // 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)
     separator_bounds.set_y(1);
 
   config.native_theme->Paint(
       canvas->sk_canvas(), ui::NativeTheme::kMenuPopupSeparator,
       ui::NativeTheme::kNormal, separator_bounds, extra);
 }
 
 }  // namespace views