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

chrome/browser/extensions/extension_settings_storage.cc

Index: chrome/browser/extensions/extension_settings_storage.cc
diff --git a/chrome/browser/extensions/extension_settings_storage.cc b/chrome/browser/extensions/extension_settings_storage.cc
index 882efe83e72268923482ae77ca8029b589eb93fc..42e5209d568a2cb6cec131dbe08bfdc5fe4cd6b7 100644
--- a/chrome/browser/extensions/extension_settings_storage.cc
+++ b/chrome/browser/extensions/extension_settings_storage.cc
@@ -8,11 +8,13 @@
 // 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());
 }
 
@@ -29,6 +31,36 @@ ExtensionSettingsStorage::Result::GetChangedKeys() const {
   return inner_->changed_keys_.get();
 }
 
+bool ExtensionSettingsStorage::Result::GetOldValue(
+    const std::string& key, Value** old_value) const {
+  DCHECK(!HasError());
+  DCHECK(old_value);
+  if (!inner_->changed_keys_.get()) {
+    return false;
+  }
+  if (!inner_->changed_keys_->count(key)) {
+    return inner_->settings_->GetWithoutPathExpansion(key, old_value);
+  }
+  *old_value = NULL;
+  inner_->old_settings_->GetWithoutPathExpansion(key, old_value);
+  return true;
+}
+
+bool ExtensionSettingsStorage::Result::GetNewValue(
+    const std::string& key, Value** new_value) const {
+  DCHECK(!HasError());
+  DCHECK(new_value);
+  if (!inner_->changed_keys_.get()) {
+    return false;
+  }
+  *new_value = NULL;
+  if (!inner_->settings_.get()) {
+    return true;
+  }
+  inner_->settings_->GetWithoutPathExpansion(key, new_value);
+  return true;
+}
+
 bool ExtensionSettingsStorage::Result::HasError() const {
   return !inner_->error_.empty();
 }
@@ -40,8 +72,12 @@ const std::string& ExtensionSettingsStorage::Result::GetError() const {
 
 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() {}