[login_manager] Use keygen helper to generate owner key

owner_key.cc

Index: owner_key.cc
diff --git a/owner_key.cc b/owner_key.cc
index d5d9686f1431d68c105fa82b404653c9ba84d29c..541161e2e0fd2bdb432c97c183167aac770fd7bf 100644
--- a/owner_key.cc
+++ b/owner_key.cc
@@ -10,6 +10,7 @@
 #include <base/logging.h>
 #include <base/scoped_ptr.h>
 
+#include "login_manager/child_job.h"
 #include "login_manager/nss_util.h"
 #include "login_manager/system_utils.h"
 
@@ -139,4 +140,14 @@ bool OwnerKey::Sign(const char* data,
   return true;
 }
 
+
+int OwnerKey::StartGeneration(ChildJobInterface* generator) {
+  int pid = fork();
+  if (pid == 0) {
+    generator->Run();
+    exit(1);  // Run() is not supposed to return.
+  }
+  return pid;
+}
+
 }  // namespace login_manager