Prefer ScopedNestableTaskAllower over manual save/restore

chrome/browser/ui/views/tab_contents/tab_contents_drag_win.cc

Index: chrome/browser/ui/views/tab_contents/tab_contents_drag_win.cc
diff --git a/chrome/browser/ui/views/tab_contents/tab_contents_drag_win.cc b/chrome/browser/ui/views/tab_contents/tab_contents_drag_win.cc
index 2c289cbb1d8d25ffcae92fa29967cf51291fee75..58955a22b0cdfdafdb6deb0bb788b532d59fbb6e 100644
--- a/chrome/browser/ui/views/tab_contents/tab_contents_drag_win.cc
+++ b/chrome/browser/ui/views/tab_contents/tab_contents_drag_win.cc
@@ -312,12 +312,14 @@ void TabContentsDragWin::DoDragging(const WebDropData& drop_data,
 
   // We need to enable recursive tasks on the message loop so we can get
   // updates while in the system DoDragDrop loop.
-  bool old_state = MessageLoop::current()->NestableTasksAllowed();
-  MessageLoop::current()->SetNestableTasksAllowed(true);
   DWORD effect;
-  DoDragDrop(ui::OSExchangeDataProviderWin::GetIDataObject(data), drag_source_,
-             web_drag_utils_win::WebDragOpMaskToWinDragOpMask(ops), &effect);
-  MessageLoop::current()->SetNestableTasksAllowed(old_state);
+  {
+    MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
+    DoDragDrop(ui::OSExchangeDataProviderWin::GetIDataObject(data),
+               drag_source_,
+               web_drag_utils_win::WebDragOpMaskToWinDragOpMask(ops),
+               &effect);
+  }
 
   // This works because WebDragSource::OnDragSourceDrop uses PostTask to
   // dispatch the actual event.