Update from https://crrev.com/317530

sandbox/linux/services/credentials.cc

Index: sandbox/linux/services/credentials.cc
diff --git a/sandbox/linux/services/credentials.cc b/sandbox/linux/services/credentials.cc
index e571ddec59776a58a1810b22bf83ba4c63b8ba58..ed21fd192bd0c7eda1ffaadcbf6583c26f18751d 100644
--- a/sandbox/linux/services/credentials.cc
+++ b/sandbox/linux/services/credentials.cc
@@ -114,7 +114,7 @@ bool ChrootToSafeEmptyDir() {
   int status = -1;
   PCHECK(HANDLE_EINTR(waitpid(pid, &status, 0)) == pid);
 
-  return kExitSuccess == status;
+  return WIFEXITED(status) && WEXITSTATUS(status) == kExitSuccess;
 }
 
 // CHECK() that an attempt to move to a new user namespace raised an expected
@@ -174,12 +174,14 @@ bool Credentials::CanCreateProcessInNewUserNS() {
   // have disappeared. Make sure to not do anything in the child, as this is a
   // fragile execution environment.
   if (pid == 0) {
-    _exit(0);
+    _exit(kExitSuccess);
   }
 
   // Always reap the child.
-  siginfo_t infop;
-  PCHECK(0 == HANDLE_EINTR(waitid(P_PID, pid, &infop, WEXITED)));
+  int status = -1;
+  PCHECK(HANDLE_EINTR(waitpid(pid, &status, 0)) == pid);
+  CHECK(WIFEXITED(status));
+  CHECK_EQ(kExitSuccess, WEXITSTATUS(status));
 
   // clone(2) succeeded, we can use CLONE_NEWUSER.
   return true;