views: Extract SystemMenuModel from native_menu_win.*.

ui/views/controls/menu/native_menu_win.cc

Index: ui/views/controls/menu/native_menu_win.cc
diff --git a/ui/views/controls/menu/native_menu_win.cc b/ui/views/controls/menu/native_menu_win.cc
index aa4adbde1ca7f1a795fd0247b8e720a5f7f4b7e2..1d518eac3f5e9090758dd4154e3656a3aaac1f16 100644
--- a/ui/views/controls/menu/native_menu_win.cc
+++ b/ui/views/controls/menu/native_menu_win.cc
@@ -17,6 +17,7 @@
 #include "ui/base/keycodes/keyboard_codes.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/l10n/l10n_util_win.h"
+#include "ui/base/models/menu_model.h"
 #include "ui/base/win/hwnd_util.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/font.h"
@@ -739,21 +740,6 @@ void NativeMenuWin::CreateHostWindow() {
 }
 
 ////////////////////////////////////////////////////////////////////////////////
-// SystemMenuModel:
-
-SystemMenuModel::SystemMenuModel(ui::SimpleMenuModel::Delegate* delegate)
-    : SimpleMenuModel(delegate) {
-}
-
-SystemMenuModel::~SystemMenuModel() {
-}
-
-int SystemMenuModel::GetFirstItemIndex(gfx::NativeMenu native_menu) const {
-  // We allow insertions before last item (Close).
-  return std::max(0, GetMenuItemCount(native_menu) - 1);
-}
-
-////////////////////////////////////////////////////////////////////////////////
 // MenuWrapper, public:
 
 // static