Multi-strategy based tracking.

chrome/browser/prefs/tracked/tracked_preference.h

+// Copyright 2014 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_TRACKED_PREFERENCE_H_
+#define CHROME_BROWSER_PREFS_TRACKED_TRACKED_PREFERENCE_H_
+
+class PrefHashStore;
+
+namespace base {
+class DictionaryValue;
+class Value;
+}
+
+// A TrackedPreference tracks changes to an individual preference, reporting and
+// reacting to them according to preference-specific and browser-wide policies.
+class TrackedPreference {
+ public:
+  virtual ~TrackedPreference() {}
+
+  // Updates |pref_hash_store| to reflect the preference's new |value|.
+  virtual void OnValueChanged(const base::Value* value,
+                              PrefHashStore* pref_hash_store) const = 0;
+
+  // Verifies that the value of this tracked preference in |pref_store_contents|
+  // is valid according to |pref_hash_store|. Responds to verification failures
+  // according to preference-specific and browser-wide policy and reports
+  // results to via UMA.
+  virtual void EnforceAndReport(
+      PrefHashStore* pref_hash_store,
+      base::DictionaryValue* pref_store_contents) const = 0;
+};
+
+#endif  // CHROME_BROWSER_PREFS_TRACKED_TRACKED_PREFERENCE_H_