Move common code into process_util.cc

base/process.h

Index: base/process.h
diff --git a/base/process.h b/base/process.h
index f52c455c742fba28c045f255dfafd2731d643933..096d1b3fe92ced60c8d8736d1afb61bff0a977e6 100644
--- a/base/process.h
+++ b/base/process.h
@@ -9,7 +9,7 @@
 #include "build/build_config.h"
 
 #include <sys/types.h>
-#ifdef OS_WIN
+#if defined(OS_WIN)
 #include <windows.h>
 #endif
 
@@ -28,7 +28,7 @@ const ProcessHandle kNullProcessHandle = NULL;
 typedef pid_t ProcessHandle;
 typedef pid_t ProcessId;
 const ProcessHandle kNullProcessHandle = 0;
-#endif
+#endif  // defined(OS_WIN)
 
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
 // saved_priority_ will be set to this to indicate that it's not holding