Use PlatformThreadId, not int when dealing with thread ids.

base/thread_collision_warner.cc

 // Copyright (c) 2006-2008 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/thread_collision_warner.h"
 
 #include "base/atomicops.h"
 #include "base/logging.h"
 
 namespace base {
 
 void DCheckAsserter::warn() {
   NOTREACHED() << "Thread Collision";
 }
 
+static subtle::Atomic32 CurrentThread() {
+  const PlatformThreadId current_thread_id = PlatformThread::CurrentId();
+  // We need to get the thread id into an atomic data type. This might be a
+  // truncating conversion, but any loss-of-information just increases the
+  // chance of a fault negative, not a false positive.
+  const subtle::Atomic32 atomic_thread_id =
+      static_cast<subtle::Atomic32>(current_thread_id);
+
+  return atomic_thread_id;
+}
+
 void ThreadCollisionWarner::EnterSelf() {
   // If the active thread is 0 then I'll write the current thread ID
   // if two or more threads arrive here only one will succeed to
   // write on valid_thread_id_ the current thread ID.
-  const int current_thread_id = PlatformThread::CurrentId();
+  subtle::Atomic32 current_thread_id = CurrentThread();
 
   int previous_value = subtle::NoBarrier_CompareAndSwap(&valid_thread_id_,
                                                         0,
                                                         current_thread_id);
   if (previous_value != 0 && previous_value != current_thread_id) {
     // gotcha! a thread is trying to use the same class and that is
     // not current thread.
     asserter_->warn();
   }
 
   subtle::NoBarrier_AtomicIncrement(&counter_, 1);
 }
 
 void ThreadCollisionWarner::Enter() {
-  const int current_thread_id = PlatformThread::CurrentId();
+  subtle::Atomic32 current_thread_id = CurrentThread();
 
   if (subtle::NoBarrier_CompareAndSwap(&valid_thread_id_,
                                        0,
                                        current_thread_id) != 0) {
     // gotcha! another thread is trying to use the same class.
     asserter_->warn();
   }
 
   subtle::NoBarrier_AtomicIncrement(&counter_, 1);
 }
 
 void ThreadCollisionWarner::Leave() {
   if (subtle::Barrier_AtomicIncrement(&counter_, -1) == 0) {
     subtle::NoBarrier_Store(&valid_thread_id_, 0);
   }
 }
 
 }  // namespace base