Provide IRT process interface

src/untrusted/nacl/getpgid.c

Index: src/untrusted/nacl/getpgid.c
diff --git a/src/untrusted/nacl/chdir.c b/src/untrusted/nacl/getpgid.c
similarity index 60%
copy from src/untrusted/nacl/chdir.c
copy to src/untrusted/nacl/getpgid.c
index 2acc4c0aef86e239b0716259309e58622d9cde92..19f6011f7b2dc278a9c0fdfa1d1d0e34f4628e4f 100644
--- a/src/untrusted/nacl/chdir.c
+++ b/src/untrusted/nacl/getpgid.c
@@ -10,17 +10,18 @@
 
 #include "native_client/src/untrusted/nacl/nacl_irt.h"
 
-int chdir(const char *path) {
-  if (!__libnacl_irt_init_fn(&__libnacl_irt_dev_filename.chdir,
-                             __libnacl_irt_dev_filename_init)) {
+pid_t getpgid(pid_t pid) {
+  if (!__libnacl_irt_init_fn(&__libnacl_irt_dev_process.getpgid,
+                             __libnacl_irt_dev_process_init)) {
     return -1;
   }
 
-  int error = __libnacl_irt_dev_filename.chdir(path);
+  pid_t pgid;
+  int error = __libnacl_irt_dev_process.getpgid(pid, &pgid);
   if (error) {
     errno = error;
     return -1;
   }
 
-  return 0;
+  return pgid;
 }