Mac: Other approach for IPCing child task_ts.

chrome/browser/mach_broker_mac.h

 // Copyright (c) 2009 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 CHROME_BROWSER_MACH_BROKER_H_
 #define CHROME_BROWSER_MACH_BROKER_H_
 
 #include <map>
 
 #include <mach/mach.h>
 
 #include "base/lock.h"
 #include "base/process.h"
 #include "base/process_util.h"
 #include "base/singleton.h"
+#include "chrome/common/notification_registrar.h"
 
 // On OS X, the mach_port_t of a process is required to collect metrics about
 // the process. Running |task_for_pid()| is only allowed for privileged code.
 // However, a process has port rights to all its subprocesses, so let the
 // browser's child processes send their Mach port to the browser over IPC.
 // This way, the brower can at least collect metrics of its child processes,
 // which is what it's most interested in anyway.
 //
 // Mach ports can only be sent over Mach IPC, not over the |socketpair()| that
 // the regular IPC system uses. Hence, the child processes open a Mach
 // connection shortly after launching and ipc their mach data to the browser
 // process. This data is kept in a global |MachBroker| object.
 //
 // Since this data arrives over a separate channel, it is not available
 // immediately after a child process has been started.
-class MachBroker : public base::ProcessMetrics::PortProvider {
+class MachBroker : public base::ProcessMetrics::PortProvider,
+                   public NotificationObserver {
  public:
   // Returns the global MachBroker.
   static MachBroker* instance();
 
   struct MachInfo {
     MachInfo() : mach_task_(MACH_PORT_NULL) {}
 
     MachInfo& SetTask(mach_port_t task) {
       mach_task_ = task;
       return *this;
     }
 
     mach_port_t mach_task_;
   };
 
   // Adds mach info for a given pid.
   void RegisterPid(base::ProcessHandle pid, const MachInfo& mach_info);
 
   // Removes all mappings belonging to |pid| from the broker.
   void Invalidate(base::ProcessHandle pid);
 
   // Implement |ProcessMetrics::PortProvider|.
   virtual mach_port_t TaskForPid(base::ProcessHandle process) const;
 
+  // Implement |NotificationObserver|.
+  virtual void Observe(NotificationType type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details);
  private:
   // Private constructor.
-  MachBroker() {}
+  MachBroker();
+  
+  // Used to register for notifications received by NotificationObserver.
+  // Accessed only on the UI thread.
+  NotificationRegistrar registrar_;
+  
   friend struct DefaultSingletonTraits<MachBroker>;
   friend class MachBrokerTest;
 
   // Stores mach info for every process in the broker.
   typedef std::map<base::ProcessHandle, MachInfo> MachMap;
   MachMap mach_map_;
 
   // Mutex that guards |mach_map_|.
   mutable Lock lock_;
 
+  friend class RegisterNotificationTask;
   DISALLOW_COPY_AND_ASSIGN(MachBroker);
 };
 
 #endif  // CHROME_BROWSER_MACH_BROKER_H_