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

chrome/browser/ui/views/apps/app_window_desktop_window_tree_host_win.cc

 // Copyright 2014 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 "chrome/browser/ui/views/apps/app_window_desktop_window_tree_host_win.h"
 
 #include <dwmapi.h>
 
 #include "chrome/browser/ui/views/apps/chrome_native_app_window_views_win.h"
 #include "chrome/browser/ui/views/apps/glass_app_window_frame_view_win.h"
 #include "ui/base/theme_provider.h"
-#include "ui/gfx/win/dpi.h"
+#include "ui/gfx/dpi.h"
 #include "ui/views/controls/menu/native_menu_win.h"
 
 #pragma comment(lib, "dwmapi.lib")
 
 AppWindowDesktopWindowTreeHostWin::AppWindowDesktopWindowTreeHostWin(
     ChromeNativeAppWindowViewsWin* app_window,
     views::DesktopNativeWidgetAura* desktop_native_widget_aura)
     : DesktopWindowTreeHostWin(app_window->widget(),
                                desktop_native_widget_aura),
       app_window_(app_window) {
@@ skipping 45 matching lines @@
     return;
 
   MARGINS margins = {0};
 
   // If the opaque frame is visible, we use the default (zero) margins.
   // Otherwise, we need to figure out how to extend the glass in.
   if (app_window_->glass_frame_view()) {
     gfx::Insets insets = app_window_->glass_frame_view()->GetGlassInsets();
     // The DWM API's expect values in pixels. We need to convert from DIP to
     // pixels here.
-    insets = insets.Scale(gfx::win::GetDeviceScaleFactor());
+    insets = insets.Scale(gfx::GetDeviceScaleFactor());
     margins.cxLeftWidth = insets.left();
     margins.cxRightWidth = insets.right();
     margins.cyBottomHeight = insets.bottom();
     margins.cyTopHeight = insets.top();
   }
 
   DwmExtendFrameIntoClientArea(GetHWND(), &margins);
 }