Record offline histograms with suffix via Histogram::FactoryGet

components/offline_pages/client_namespace_constants.h

+// 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 COMPONENTS_OFFLINE_PAGES_CLIENT_NAMESPACE_CONSTANTS_H_
+#define COMPONENTS_OFFLINE_PAGES_CLIENT_NAMESPACE_CONSTANTS_H_
+
+#include "build/build_config.h"
+
+namespace offline_pages {
+
+// Any changes to these well-known namespaces should also be reflected in
+// OfflinePagesNamespace (histograms.xml) for consistency.
+extern const char kBookmarkNamespace[];
+extern const char kLastNNamespace[];
+
+// Currently used for fallbacks like tests.
+extern const char kDefaultNamespace[];
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_CLIENT_NAMESPACE_CONSTANTS_H_