Allow child processes to abort quitting.

base/message_loop.h

 // Copyright (c) 2011 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.
 
 #ifndef BASE_MESSAGE_LOOP_H_
 #define BASE_MESSAGE_LOOP_H_
 #pragma once
 
 #include <queue>
 #include <string>
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   // that doing so is fairly dangerous if the target thread makes nested calls
   // to MessageLoop::Run.  The problem being that you won't know which nested
   // run loop you are quiting, so be careful!
   //
   void Quit();
 
   // This method is a variant of Quit, that does not wait for pending messages
   // to be processed before returning from Run.
   void QuitNow();
 
+  // Cancels the signal to quit once the pending messages are processed.  This
+  // method may only be called on the same thread that called Run, and Run must
+  // still be on the call stack.
+  void CancelQuit();
+
   // Invokes Quit on the current MessageLoop when run.  Useful to schedule an
   // arbitrary MessageLoop to Quit.
   class QuitTask : public Task {
    public:
     virtual void Run() {
       MessageLoop::current()->Quit();
     }
   };
 
   // Returns the type passed to the constructor.
@@ skipping 428 matching lines @@
 #endif  // defined(OS_POSIX)
 };
 
 // Do not add any member variables to MessageLoopForIO!  This is important b/c
 // MessageLoopForIO is often allocated via MessageLoop(TYPE_IO).  Any extra
 // data that you need should be stored on the MessageLoop's pump_ instance.
 COMPILE_ASSERT(sizeof(MessageLoop) == sizeof(MessageLoopForIO),
                MessageLoopForIO_should_not_have_extra_member_variables);
 
 #endif  // BASE_MESSAGE_LOOP_H_