Use portable typedef for PIDs (process IDs).

base/process_posix.cc

 // Copyright (c) 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/process.h"
 #include "base/process_util.h"
 
 namespace base {
 
 void Process::Close() {
@@ skipping 32 matching lines @@
 bool Process::UnReduceWorkingSet() {
   // http://code.google.com/p/chromium/issues/detail?id=8083
   return false;
 }
 
 bool Process::EmptyWorkingSet() {
   // http://code.google.com/p/chromium/issues/detail?id=8083
   return false;
 }
 
-int32 Process::pid() const {
+ProcessId Process::pid() const {
   if (process_ == 0)
     return 0;
 
   return GetProcId(process_);
 }
 
 bool Process::is_current() const {
   return process_ == GetCurrentProcessHandle();
 }
 
 // static
 Process Process::Current() {
   return Process(GetCurrentProcessHandle());
 }
 
 }  // namspace base