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

ui/views/win/hwnd_message_handler.cc

Index: ui/views/win/hwnd_message_handler.cc
diff --git a/ui/views/win/hwnd_message_handler.cc b/ui/views/win/hwnd_message_handler.cc
index 1544507ef39740982de458fcff8f71dd0b069b6c..dfe4dc214dbb540998ec1ef641530f3a0d660349 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -26,12 +26,12 @@
 #include "ui/events/keycodes/keyboard_code_conversion_win.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/canvas_skia_paint.h"
+#include "ui/gfx/dpi.h"
 #include "ui/gfx/icon_util.h"
 #include "ui/gfx/insets.h"
 #include "ui/gfx/path.h"
 #include "ui/gfx/path_win.h"
 #include "ui/gfx/screen.h"
-#include "ui/gfx/win/dpi.h"
 #include "ui/gfx/win/hwnd_util.h"
 #include "ui/native_theme/native_theme_win.h"
 #include "ui/views/views_delegate.h"
@@ -1219,7 +1219,7 @@ void HWNDMessageHandler::RedrawLayeredWindowContents() {
 
   // We need to clip to the dirty rect ourselves.
   layered_window_contents_->sk_canvas()->save();
-  double scale = gfx::win::GetDeviceScaleFactor();
+  double scale = gfx::GetDeviceScaleFactor();
   layered_window_contents_->sk_canvas()->scale(
       SkScalar(scale),SkScalar(scale));
   layered_window_contents_->ClipRect(invalid_rect_);
@@ -1418,8 +1418,8 @@ void HWNDMessageHandler::OnGetMinMaxInfo(MINMAXINFO* minmax_info) {
   gfx::Size min_window_size;
   gfx::Size max_window_size;
   delegate_->GetMinMaxSize(&min_window_size, &max_window_size);
-  min_window_size = gfx::win::DIPToScreenSize(min_window_size);
-  max_window_size = gfx::win::DIPToScreenSize(max_window_size);
+  min_window_size = gfx::DIPToScreenSize(min_window_size);
+  max_window_size = gfx::DIPToScreenSize(max_window_size);
 
 
   // Add the native frame border size to the minimum and maximum size if the