Add onChanged events to the extension settings API, both from sync and between

chrome/browser/extensions/extension_settings_storage.cc

 // 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 "base/logging.h"
 #include "chrome/browser/extensions/extension_settings_storage.h"
 
 // Implementation of ExtensionSettingsStorage::Result
 
 ExtensionSettingsStorage::Result::Result(
-    DictionaryValue* settings, std::set<std::string>* changed_keys)
-    : inner_(new Inner(settings, changed_keys, std::string())) {}
+    DictionaryValue* settings,
+    DictionaryValue* old_settings,
+    std::set<std::string>* changed_keys)
+    : inner_(new Inner(settings, old_settings, changed_keys, std::string())) {}
 
 ExtensionSettingsStorage::Result::Result(const std::string& error)
-    : inner_(new Inner(NULL, new std::set<std::string>(), error)) {
+    : inner_(new Inner(NULL, NULL, new std::set<std::string>(), error)) {
   DCHECK(!error.empty());
 }
 
 ExtensionSettingsStorage::Result::~Result() {}
 
-DictionaryValue* ExtensionSettingsStorage::Result::GetSettings() const {
+const DictionaryValue* ExtensionSettingsStorage::Result::GetSettings() const {
   DCHECK(!HasError());
   return inner_->settings_.get();
 }
 
-std::set<std::string>*
+const std::set<std::string>*
 ExtensionSettingsStorage::Result::GetChangedKeys() const {
   DCHECK(!HasError());
   return inner_->changed_keys_.get();
 }
 
+const Value* ExtensionSettingsStorage::Result::GetOldValue(
+    const std::string& key) const {
+  DCHECK(!HasError());
+  if (!inner_->changed_keys_.get()) {
+    return NULL;
+  }
+  Value* old_value = NULL;
+  if (inner_->changed_keys_->count(key)) {
+    inner_->old_settings_->GetWithoutPathExpansion(key, &old_value);
+  } else if (inner_->settings_.get()) {
+    inner_->settings_->GetWithoutPathExpansion(key, &old_value);
+  }
+  return old_value;
+}
+
+const Value* ExtensionSettingsStorage::Result::GetNewValue(
+    const std::string& key) const {
+  DCHECK(!HasError());
+  if (!inner_->changed_keys_.get()) {
+    return NULL;
+  }
+  Value* new_value = NULL;
+  if (inner_->settings_.get()) {
+    inner_->settings_->GetWithoutPathExpansion(key, &new_value);
+  }
+  return new_value;
+}
+
 bool ExtensionSettingsStorage::Result::HasError() const {
   return !inner_->error_.empty();
 }
 
 const std::string& ExtensionSettingsStorage::Result::GetError() const {
   DCHECK(HasError());
   return inner_->error_;
 }
 
 ExtensionSettingsStorage::Result::Inner::Inner(
     DictionaryValue* settings,
+    DictionaryValue* old_settings,
     std::set<std::string>* changed_keys,
     const std::string& error)
-    : settings_(settings), changed_keys_(changed_keys), error_(error) {}
+    : settings_(settings),
+      old_settings_(old_settings),
+      changed_keys_(changed_keys),
+      error_(error) {}
 
 ExtensionSettingsStorage::Result::Inner::~Inner() {}