Record offline histograms with suffix via Histogram::FactoryGet

components/offline_pages/client_namespace_constants.h

Index: components/offline_pages/client_namespace_constants.h
diff --git a/components/offline_pages/client_namespace_constants.h b/components/offline_pages/client_namespace_constants.h
new file mode 100644
index 0000000000000000000000000000000000000000..108e031516d6b6eee963f0cd7d2629f84fdfd809
--- /dev/null
+++ b/components/offline_pages/client_namespace_constants.h
@@ -0,0 +1,22 @@
+// 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[];

[dewittj, 2016/05/31 22:38:45]

can't this just be constexpr char kBookmarkNamespace[] = "foo";?

[jianli, 2016/05/31 23:50:08]

Yes, it would work. But we don't really needs their content in header file,
right? If so, it is suggested to still put it in .cc file.

+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_