Mac build fix

base/waitable_event.h

 // 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.
 
 #ifndef BASE_WAITABLE_EVENT_H_
 #define BASE_WAITABLE_EVENT_H_
 
 #include "base/basictypes.h"
 
 #if defined(OS_WIN)
@@ skipping 118 matching lines @@
   bool SignalOne();
   void Enqueue(Waiter* waiter);
   bool Dequeue(Waiter* waiter, void* tag);
 
   // When dealing with arrays of WaitableEvent*, we want to sort by the address
   // of the WaitableEvent in order to have a globally consistent locking order.
   // In that case we keep them, in sorted order, in an array of pairs where the
   // second element is the index of the WaitableEvent in the original,
   // unsorted, array.
   typedef std::pair<WaitableEvent*, size_t> WaiterAndIndex;
-  static unsigned EnqueueMany(WaiterAndIndex* waitables,
-                              size_t count, Waiter* waiter);
+  static size_t EnqueueMany(WaiterAndIndex* waitables,
+                            size_t count, Waiter* waiter);
 
   Lock lock_;
   bool signaled_;
   const bool manual_reset_;
   std::list<Waiter*> waiters_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(WaitableEvent);
 };
 
 }  // namespace base
 
 #endif  // BASE_WAITABLE_EVENT_H_