Introduce UserHiveVisitor for performing operations on local users' registry hives.

chrome/installer/setup/user_hive_visitor.h

Index: chrome/installer/setup/user_hive_visitor.h
diff --git a/chrome/installer/setup/user_hive_visitor.h b/chrome/installer/setup/user_hive_visitor.h
new file mode 100644
index 0000000000000000000000000000000000000000..e57358d2a818262ac5a0d6fbc8b3277c18c0a8df
--- /dev/null
+++ b/chrome/installer/setup/user_hive_visitor.h
@@ -0,0 +1,30 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_INSTALLER_SETUP_USER_HIVE_VISITOR_H_
+#define CHROME_INSTALLER_SETUP_USER_HIVE_VISITOR_H_
+
+#include "base/callback_forward.h"
+
+namespace base {
+namespace win {
+class RegKey;
+}
+}
+
+namespace installer {
+
+// The visitor callback invoked for each user's registry hive by
+// |VisitUserHives|. The first argument is the user SID being visited, while the
+// second is the root of that user's registry hive. Implementations return
+// |true| to indicate that the visits should continue, or |false| to indicate
+// that visits should stop.
+using HiveVisitor = base::Callback<bool(const wchar_t*, base::win::RegKey*)>;

[gab, 2016/06/01 14:34:44]

Name parameters here and use their names in comment above.

[grt (UTC plus 2), 2016/06/01 14:40:38]

Done.

+
+// Runs |visitor| for each local user profile's registry hive.
+void VisitUserHives(const HiveVisitor& visitor);
+
+}  // namespace installer
+
+#endif  // CHROME_INSTALLER_SETUP_USER_HIVE_VISITOR_H_