base: Re-apply WeakPtr support for SequencedWorkerPools, fixing deadlock

base/message_loop/message_pump_io_ios.h

 // Copyright 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.
 
 #ifndef BASE_MESSAGE_LOOP_MESSAGE_PUMP_IO_IOS_H_
 #define BASE_MESSAGE_LOOP_MESSAGE_PUMP_IO_IOS_H_
 
 #include "base/base_export.h"
 #include "base/mac/scoped_cffiledescriptorref.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_pump_mac.h"
 #include "base/observer_list.h"
+#include "base/threading/thread_checker.h"
 
 namespace base {
 
 // This file introduces a class to monitor sockets and issue callbacks when
 // sockets are ready for I/O on iOS.
 class BASE_EXPORT MessagePumpIOSForIO : public MessagePumpNSRunLoop {
  public:
   class IOObserver {
    public:
     IOObserver() {}
@@ skipping 109 matching lines @@
   ThreadChecker watch_file_descriptor_caller_checker_;
 
   base::WeakPtrFactory<MessagePumpIOSForIO> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MessagePumpIOSForIO);
 };
 
 }  // namespace base
 
 #endif  // BASE_MESSAGE_LOOP_MESSAGE_PUMP_IO_IOS_H_