Use portable typedef for PIDs (process IDs).

base/process.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_PROCESS_H_
 #define BASE_PROCESS_H_
 
 #include "base/basictypes.h"
 
+#include <sys/types.h>
 #ifdef OS_WIN
 #include <windows.h>
 #endif
 
 namespace base {
 
 // ProcessHandle is a platform specific type which represents the underlying OS
 // handle to a process.
+// ProcessId is a number which identifies the process in the OS.
 #if defined(OS_WIN)
 typedef HANDLE ProcessHandle;
+typedef DWORD ProcessId;
 #elif defined(OS_POSIX)
 // On POSIX, our ProcessHandle will just be the PID.
-typedef int ProcessHandle;
+typedef pid_t ProcessHandle;
+typedef pid_t ProcessId;
 #endif
 
 class Process {
  public:
   Process() : process_(0), last_working_set_size_(0) {}
   explicit Process(ProcessHandle handle) :
     process_(handle), last_working_set_size_(0) {}
 
   // A handle to the current process.
   static Process Current();
 
   // Get/Set the handle for this process. The handle will be 0 if the process
   // is no longer running.
   ProcessHandle handle() const { return process_; }
   void set_handle(ProcessHandle handle) { process_ = handle; }
 
   // Get the PID for this process.
-  int32 pid() const;
+  ProcessId pid() const;
 
   // Is the this process the current process.
   bool is_current() const;
 
   // Close the process handle. This will not terminate the process.
   void Close();
 
   // Terminates the process with extreme prejudice. The given result code will
   // be the exit code of the process. If the process has already exited, this
   // will do nothing.
@@ skipping 29 matching lines @@
   bool EmptyWorkingSet();
 
  private:
   ProcessHandle process_;
   size_t last_working_set_size_;
 };
 
 }  // namespace base
 
 #endif  // BASE_PROCESS_H_