Revert of Move base/prefs to components/prefs

base/prefs/overlay_user_pref_store.h

Index: base/prefs/overlay_user_pref_store.h
diff --git a/base/prefs/overlay_user_pref_store.h b/base/prefs/overlay_user_pref_store.h
index 594c50105f8c9e156a3879f79de4367111d8dec4..35ada57123f785e79b8ad099481e5538e4f90552 100644
--- a/base/prefs/overlay_user_pref_store.h
+++ b/base/prefs/overlay_user_pref_store.h
@@ -2,6 +2,88 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// TODO(brettw) remove this forwarding header when prefs is completely moved to
-// components.
-#include "components/prefs/overlay_user_pref_store.h"
+#ifndef BASE_PREFS_OVERLAY_USER_PREF_STORE_H_
+#define BASE_PREFS_OVERLAY_USER_PREF_STORE_H_
+
+#include <stdint.h>
+
+#include <map>
+#include <string>
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/observer_list.h"
+#include "base/prefs/base_prefs_export.h"
+#include "base/prefs/persistent_pref_store.h"
+#include "base/prefs/pref_value_map.h"
+
+// PersistentPrefStore that directs all write operations into an in-memory
+// PrefValueMap. Read operations are first answered by the PrefValueMap.
+// If the PrefValueMap does not contain a value for the requested key,
+// the look-up is passed on to an underlying PersistentPrefStore |underlay_|.
+class BASE_PREFS_EXPORT OverlayUserPrefStore : public PersistentPrefStore,
+                                               public PrefStore::Observer {
+ public:
+  explicit OverlayUserPrefStore(PersistentPrefStore* underlay);
+
+  // Returns true if a value has been set for the |key| in this
+  // OverlayUserPrefStore, i.e. if it potentially overrides a value
+  // from the |underlay_|.
+  virtual bool IsSetInOverlay(const std::string& key) const;
+
+  // Methods of PrefStore.
+  void AddObserver(PrefStore::Observer* observer) override;
+  void RemoveObserver(PrefStore::Observer* observer) override;
+  bool HasObservers() const override;
+  bool IsInitializationComplete() const override;
+  bool GetValue(const std::string& key,
+                const base::Value** result) const override;
+
+  // Methods of PersistentPrefStore.
+  bool GetMutableValue(const std::string& key, base::Value** result) override;
+  void SetValue(const std::string& key,
+                scoped_ptr<base::Value> value,
+                uint32_t flags) override;
+  void SetValueSilently(const std::string& key,
+                        scoped_ptr<base::Value> value,
+                        uint32_t flags) override;
+  void RemoveValue(const std::string& key, uint32_t flags) override;
+  bool ReadOnly() const override;
+  PrefReadError GetReadError() const override;
+  PrefReadError ReadPrefs() override;
+  void ReadPrefsAsync(ReadErrorDelegate* delegate) override;
+  void CommitPendingWrite() override;
+  void SchedulePendingLossyWrites() override;
+  void ReportValueChanged(const std::string& key, uint32_t flags) override;
+
+  // Methods of PrefStore::Observer.
+  void OnPrefValueChanged(const std::string& key) override;
+  void OnInitializationCompleted(bool succeeded) override;
+
+  void RegisterOverlayPref(const std::string& key);
+  void RegisterOverlayPref(const std::string& overlay_key,
+                           const std::string& underlay_key);
+
+ protected:
+  ~OverlayUserPrefStore() override;
+
+ private:
+  typedef std::map<std::string, std::string> NamesMap;
+
+  const std::string& GetOverlayKey(const std::string& underlay_key) const;
+  const std::string& GetUnderlayKey(const std::string& overlay_key) const;
+
+  // Returns true if |key| corresponds to a preference that shall be stored in
+  // an in-memory PrefStore that is not persisted to disk.
+  bool ShallBeStoredInOverlay(const std::string& key) const;
+
+  base::ObserverList<PrefStore::Observer, true> observers_;
+  PrefValueMap overlay_;
+  scoped_refptr<PersistentPrefStore> underlay_;
+  NamesMap overlay_to_underlay_names_map_;
+  NamesMap underlay_to_overlay_names_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(OverlayUserPrefStore);
+};
+
+#endif  // BASE_PREFS_OVERLAY_USER_PREF_STORE_H_