Take out and generalize user prefs overriding from IncognitoUserPrefStore.

chrome/browser/prefs/overlay_user_pref_store.cc

Index: chrome/browser/prefs/overlay_user_pref_store.cc
diff --git a/chrome/browser/prefs/overlay_user_pref_store.cc b/chrome/browser/prefs/overlay_user_pref_store.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8796b405470afdc2fefa13552f52467b23187265
--- /dev/null
+++ b/chrome/browser/prefs/overlay_user_pref_store.cc
@@ -0,0 +1,183 @@
+// Copyright (c) 2011 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.
+
+#include "chrome/browser/prefs/incognito_user_pref_store.h"
+
+#include "base/memory/scoped_ptr.h"
+#include "base/values.h"
+
+OverlayUserPrefStore::OverlayUserPrefStore(
+    PersistentPrefStore* underlay)
+    : underlay_(underlay) {
+  underlay_->AddObserver(this);
+}
+
+OverlayUserPrefStore::~OverlayUserPrefStore() {
+  underlay_->RemoveObserver(this);
+}
+
+bool OverlayUserPrefStore::IsSetInOverlay(const std::string& key) const {
+  return overlay_.GetValue(key, NULL);
+}
+
+void OverlayUserPrefStore::AddObserver(PrefStore::Observer* observer) {
+  observers_.AddObserver(observer);
+}
+
+void OverlayUserPrefStore::RemoveObserver(PrefStore::Observer* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+bool OverlayUserPrefStore::IsInitializationComplete() const {
+  return underlay_->IsInitializationComplete();
+}
+
+PrefStore::ReadResult OverlayUserPrefStore::GetValue(
+    const std::string& key,
+    const Value** result) const {
+  // If the |key| shall NOT be stored in the overlay store, there must not
+  // be an entry.
+  DCHECK(ShallBeStoredInOverlay(key) || !overlay_.GetValue(key, NULL));
+
+  if (overlay_.GetValue(key, result))
+    return READ_OK;
+  return underlay_->GetValue(GetUnderlayKey(key), result);
+}
+
+PrefStore::ReadResult OverlayUserPrefStore::GetMutableValue(
+    const std::string& key,
+    Value** result) {
+  if (!ShallBeStoredInOverlay(key))
+    return underlay_->GetMutableValue(GetUnderlayKey(key), result);
+
+  if (overlay_.GetValue(key, result))
+    return READ_OK;
+
+  // Try to create copy of underlay if the overlay does not contain a value.
+  Value* underlay_value = NULL;
+  PrefStore::ReadResult read_result =
+      underlay_->GetMutableValue(GetUnderlayKey(key), &underlay_value);
+  if (read_result != READ_OK)
+    return read_result;
+
+  *result = underlay_value->DeepCopy();
+  overlay_.SetValue(key, *result);
+  return READ_OK;
+}
+
+void OverlayUserPrefStore::SetValue(const std::string& key,
+                                      Value* value) {
+  if (!ShallBeStoredInOverlay(key)) {
+    underlay_->SetValue(GetUnderlayKey(key), value);
+    return;
+  }
+
+  if (overlay_.SetValue(key, value))
+    ReportValueChanged(key);
+}
+
+void OverlayUserPrefStore::SetValueSilently(const std::string& key,
+                                              Value* value) {
+  if (!ShallBeStoredInOverlay(key)) {
+    underlay_->SetValueSilently(GetUnderlayKey(key), value);
+    return;
+  }
+
+  overlay_.SetValue(key, value);
+}
+
+void OverlayUserPrefStore::RemoveValue(const std::string& key) {
+  if (!ShallBeStoredInOverlay(key)) {
+    underlay_->RemoveValue(GetUnderlayKey(key));
+    return;
+  }
+
+  if (overlay_.RemoveValue(key))
+    ReportValueChanged(key);
+}
+
+bool OverlayUserPrefStore::ReadOnly() const {
+  return false;
+}
+
+PersistentPrefStore::PrefReadError OverlayUserPrefStore::ReadPrefs() {
+  // We do not read intentionally.
+  OnInitializationCompleted(true);
+  return PersistentPrefStore::PREF_READ_ERROR_NONE;
+}
+
+void OverlayUserPrefStore::ReadPrefsAsync(
+    ReadErrorDelegate* error_delegate_raw) {
+  scoped_ptr<ReadErrorDelegate> error_delegate(error_delegate_raw);
+  // We do not read intentionally.
+  OnInitializationCompleted(true);
+}
+
+bool OverlayUserPrefStore::WritePrefs() {
+  // We do not write our content intentionally.
+  return true;
+}
+
+void OverlayUserPrefStore::ScheduleWritePrefs() {
+  underlay_->ScheduleWritePrefs();
+  // We do not write our content intentionally.
+}
+
+void OverlayUserPrefStore::CommitPendingWrite() {
+  underlay_->CommitPendingWrite();
+  // We do not write our content intentionally.
+}
+
+void OverlayUserPrefStore::ReportValueChanged(const std::string& key) {
+  FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
+}
+
+void OverlayUserPrefStore::RegisterOverlayProperty(const std::string& key) {
+  RegisterOverlayProperty(key, key);
+}
+
+void OverlayUserPrefStore::RegisterOverlayProperty(
+    const std::string& overlay_key,
+    const std::string& underlay_key) {
+  DCHECK(!overlay_key.empty()) << "Overlay key is empty";
+  DCHECK(overlay_to_underlay_names_map_.find(overlay_key) ==
+         overlay_to_underlay_names_map_.end()) <<
+      "Overlay key already registered";
+  DCHECK(!underlay_key.empty()) << "Underlay key is empty";
+  DCHECK(underlay_to_overlay_names_map_.find(underlay_key) ==
+         underlay_to_overlay_names_map_.end()) <<
+      "Underlay key already registered";
+  overlay_to_underlay_names_map_[overlay_key] = underlay_key;
+  underlay_to_overlay_names_map_[underlay_key] = overlay_key;
+}
+
+void OverlayUserPrefStore::OnPrefValueChanged(const std::string& key) {
+  if (!overlay_.GetValue(GetOverlayKey(key), NULL))
+    ReportValueChanged(GetOverlayKey(key));
+}
+
+void OverlayUserPrefStore::OnInitializationCompleted(bool succeeded) {
+  FOR_EACH_OBSERVER(PrefStore::Observer, observers_,
+                    OnInitializationCompleted(succeeded));
+}
+
+const std::string& OverlayUserPrefStore::GetOverlayKey(
+    const std::string& underlay_key) const {
+  NamesMap::const_iterator i =
+      underlay_to_overlay_names_map_.find(underlay_key);
+  return i != underlay_to_overlay_names_map_.end() ? i->second : underlay_key;
+}
+
+const std::string& OverlayUserPrefStore::GetUnderlayKey(
+    const std::string& overlay_key) const {
+  NamesMap::const_iterator i =
+      overlay_to_underlay_names_map_.find(overlay_key);
+  return i != overlay_to_underlay_names_map_.end() ? i->second : overlay_key;
+}
+
+bool OverlayUserPrefStore::ShallBeStoredInOverlay(
+    const std::string& key) const {
+  return overlay_to_underlay_names_map_.find(key) !=
+      overlay_to_underlay_names_map_.end();
+}