Multi-strategy based tracking.

chrome/browser/prefs/tracked_split_preference.h

+// Copyright 2013 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_BROWSER_PREFS_TRACKED_SPLIT_PREFERENCE_H_
+#define CHROME_BROWSER_PREFS_TRACKED_SPLIT_PREFERENCE_H_
+
+#include <string>
+
+#include "chrome/browser/prefs/tracked_preference.h"
+
+// A TrackedSplitPreference must be tracking a dictionary pref. Each top-level
+// entry in its dictionary is tracked and enforced independently.
+// Note: preferences using this strategy must be kept in sync with
+// TrackedSplitPreferences in histograms.xml.
+class TrackedSplitPreference : public TrackedPreference {
+ public:
+  // Constructs a TrackedSplitPreference. |pref_path| must be a dictionary pref.
+  TrackedSplitPreference(const std::string& pref_path,
+                         size_t reporting_id,
+                         size_t reporting_ids_count,
+                         EnforcementLevel enforcement_level);
+
+  // TrackedPreference implementation.
+  virtual void StoreHash(const base::Value* value,
+                         PrefHashStore* pref_hash_store) const OVERRIDE;
+  virtual void EnforceAndReport(
+      PrefHashStore* pref_hash_store,
+      base::DictionaryValue* pref_store_contents) const OVERRIDE;
+
+ private:
+  // Reports, via UMA, the |count| of split preference entry that were
+  // considered invalid in a CHANGED event.
+  void ReportSplitPreferenceChangedCount(size_t count) const;
+
+  const std::string pref_path_;
+
+  DISALLOW_COPY_AND_ASSIGN(TrackedSplitPreference);
+};
+
+#endif  // CHROME_BROWSER_PREFS_TRACKED_SPLIT_PREFERENCE_H_