Make the MessageLoop PostTask ID more unique.

base/message_loop/message_loop.cc

 // Copyright 2013 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 "base/message_loop/message_loop.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
@@ skipping 521 matching lines @@
   // absolutely "correct" behavior.  See TODO above about deleting all tasks
   // when it's safe.
   while (!delayed_work_queue_.empty()) {
     delayed_work_queue_.pop();
   }
   return did_work;
 }
 
 uint64 MessageLoop::GetTaskTraceID(const PendingTask& task) {
   return (static_cast<uint64>(task.sequence_num) << 32) |
-         static_cast<uint64>(reinterpret_cast<intptr_t>(this));
+         ((static_cast<uint64>(reinterpret_cast<intptr_t>(this)) << 32) >> 32);
 }
 
 void MessageLoop::ReloadWorkQueue() {
   // We can improve performance of our loading tasks from the incoming queue to
   // |*work_queue| by waiting until the last minute (|*work_queue| is empty) to
   // load. That reduces the number of locks-per-task significantly when our
   // queues get large.
   if (work_queue_.empty())
     incoming_task_queue_->ReloadWorkQueue(&work_queue_);
 }
@@ skipping 192 matching lines @@
       fd,
       persistent,
       mode,
       controller,
       delegate);
 }
 
 #endif
 
 }  // namespace base