Prefer ScopedNestableTaskAllower over manual save/restore

chrome/browser/printing/print_view_manager.cc

 // Copyright (c) 2012 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/printing/print_view_manager.h"
 
 #include <map>
 
 #include "base/bind.h"
 #include "base/lazy_instance.h"
@@ skipping 528 matching lines @@
   // can be dead slow. On the other side, we don't want to die infinitely for a
   // real network error. Give the printer 60 seconds to comply.
   //
   // - If we're looping because of renderer page generation, the renderer could
   // be CPU bound, the page overly complex/large or the system just
   // memory-bound.
   static const int kPrinterSettingsTimeout = 60000;
   base::OneShotTimer<MessageLoop> quit_timer;
   quit_timer.Start(FROM_HERE,
                    TimeDelta::FromMilliseconds(kPrinterSettingsTimeout),
                    MessageLoop::current(), &MessageLoop::Quit);

[jar (doing other things), 2012/02/11 03:24:38]

(again, orthogonal to your CL):

This is a terrible and risky pattern.  The quit message can terminate *any*
nested message loop, and not just the one that is visible in line 556.

[dhollowa, 2012/02/13 17:44:26]

(Also added by Darin.)

[jar (doing other things), 2012/02/13 18:03:02]

Darin,

Was this your code?  (or you just updated it).  

Is there a bug to remove it?

Thanks,

Jim

On 2012/02/13 17:44:26, dhollowa wrote:

 
   inside_inner_message_loop_ = true;
 
   // Need to enable recursive task.
-  bool old_state = MessageLoop::current()->NestableTasksAllowed();
-  MessageLoop::current()->SetNestableTasksAllowed(true);
-  MessageLoop::current()->Run();
-  // Restore task state.
-  MessageLoop::current()->SetNestableTasksAllowed(old_state);
+  {
+    MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
+    MessageLoop::current()->Run();
+  }
 
   bool success = true;
   if (inside_inner_message_loop_) {
     // Ok we timed out. That's sad.
     inside_inner_message_loop_ = false;
     success = false;
   }
 
   return success;
 }
@@ skipping 29 matching lines @@
 }
 
 bool PrintViewManager::PrintNowInternal(IPC::Message* message) {
   // Don't print / print preview interstitials.
   if (web_contents()->ShowingInterstitialPage())
     return false;
   return Send(message);
 }
 
 }  // namespace printing