Use portable typedef for PIDs (process IDs).

This is a preparation to land http://codereview.chromium.org/54003,
which replaces chrome_process_filter with more portable chrome_process_util.

Review URL: http://codereview.chromium.org/57062

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@12948 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/base/process_win.cc b/base/process_win.cc
index 697a020..98a7f46c6 100644
--- a/base/process_win.cc
+++ b/base/process_win.cc
@@ -107,7 +107,7 @@
   return rv == TRUE;
 }
 
-int32 Process::pid() const {
+ProcessId Process::pid() const {
   if (process_ == 0)
     return 0;