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

ui/gfx/screen_win.cc

Index: ui/gfx/screen_win.cc
diff --git a/ui/gfx/screen_win.cc b/ui/gfx/screen_win.cc
index a115a104752411eb7d0858c9b181717b75789d8e..27122645b97148241f34c950cf55ddf369d787b9 100644
--- a/ui/gfx/screen_win.cc
+++ b/ui/gfx/screen_win.cc
@@ -11,7 +11,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/win_util.h"
 #include "ui/gfx/display.h"
-#include "ui/gfx/win/dpi.h"
+#include "ui/gfx/dpi.h"
 
 namespace {
 
@@ -29,7 +29,7 @@ gfx::Display GetDisplay(MONITORINFOEX& monitor_info) {
   gfx::Rect bounds = gfx::Rect(monitor_info.rcMonitor);
   gfx::Display display(id, bounds);
   display.set_work_area(gfx::Rect(monitor_info.rcWork));
-  display.SetScaleAndBounds(gfx::win::GetDeviceScaleFactor(), bounds);
+  display.SetScaleAndBounds(gfx::GetDeviceScaleFactor(), bounds);
 
   DEVMODE mode;
   memset(&mode, 0, sizeof(DEVMODE));
@@ -101,7 +101,7 @@ gfx::Point ScreenWin::GetCursorScreenPoint() {
   POINT pt;
   GetCursorPos(&pt);
   gfx::Point cursor_pos_pixels(pt);
-  return gfx::win::ScreenToDIPPoint(cursor_pos_pixels);
+  return gfx::ScreenToDIPPoint(cursor_pos_pixels);
 }
 
 gfx::NativeWindow ScreenWin::GetWindowUnderCursor() {
@@ -111,7 +111,7 @@ gfx::NativeWindow ScreenWin::GetWindowUnderCursor() {
 }
 
 gfx::NativeWindow ScreenWin::GetWindowAtScreenPoint(const gfx::Point& point) {
-  gfx::Point point_in_pixels = gfx::win::DIPToScreenPoint(point);
+  gfx::Point point_in_pixels = gfx::DIPToScreenPoint(point);
   return GetNativeWindowFromHWND(WindowFromPoint(point_in_pixels.ToPOINT()));
 }