forwarder2: Make the Forwarder instances operate on a single thread.

tools/android/forwarder2/pipe_notifier.h

 // 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.
 
 #ifndef TOOLS_ANDROID_FORWARDER2_PIPE_NOTIFIER_H_
 #define TOOLS_ANDROID_FORWARDER2_PIPE_NOTIFIER_H_
 
 #include "base/basictypes.h"
 
 namespace forwarder2 {
 
 // Helper class used to create a unix pipe that sends notifications to the
 // |receiver_fd_| file descriptor when called |Notify()|.  This should be used
 // by the main thread to notify other threads that it must exit.
 // The |receiver_fd_| can be put into a fd_set and used in a select together
 // with a socket waiting to accept or read.
 class PipeNotifier {
  public:
   PipeNotifier();
   ~PipeNotifier();
 
   bool Notify();
 
   int receiver_fd() const { return receiver_fd_; }
 
+  void Reset();
+
  private:
   int sender_fd_;
   int receiver_fd_;
 
   DISALLOW_COPY_AND_ASSIGN(PipeNotifier);
 };
 
 }  // namespace forwarder
 
 #endif  // TOOLS_ANDROID_FORWARDER2_PIPE_NOTIFIER_H_