Fix race condition in MD Settings Languages page causing inconsistent settings

chrome/browser/extensions/api/language_settings_private/language_settings_private_api.cc

Index: chrome/browser/extensions/api/language_settings_private/language_settings_private_api.cc
diff --git a/chrome/browser/extensions/api/language_settings_private/language_settings_private_api.cc b/chrome/browser/extensions/api/language_settings_private/language_settings_private_api.cc
index efc2f1ff66bc86a58ef29f16cf8c01cf78a62947..b099c3ed2627f5073f46d6669eb6a26b2687838c 100644
--- a/chrome/browser/extensions/api/language_settings_private/language_settings_private_api.cc
+++ b/chrome/browser/extensions/api/language_settings_private/language_settings_private_api.cc
@@ -245,26 +245,70 @@ LanguageSettingsPrivateGetLanguageListFunction::Run() {
   return RespondNow(OneArgument(std::move(language_list)));
 }
 
-LanguageSettingsPrivateSetLanguageListFunction::
-    LanguageSettingsPrivateSetLanguageListFunction()
-    : chrome_details_(this) {
-}
+LanguageSettingsPrivateEnableLanguageFunction::
+    LanguageSettingsPrivateEnableLanguageFunction()
+    : chrome_details_(this) {}
+
+LanguageSettingsPrivateEnableLanguageFunction::
+    ~LanguageSettingsPrivateEnableLanguageFunction() {}
+
+ExtensionFunction::ResponseAction
+LanguageSettingsPrivateEnableLanguageFunction::Run() {
+  std::unique_ptr<language_settings_private::EnableLanguage::Params>
+      parameters =
+          language_settings_private::EnableLanguage::Params::Create(*args_);
+  EXTENSION_FUNCTION_VALIDATE(parameters.get());
+  const std::string& language_code = parameters->language_code;
+
+  std::unique_ptr<translate::TranslatePrefs> translate_prefs =
+      ChromeTranslateClient::CreateTranslatePrefs(
+          chrome_details_.GetProfile()->GetPrefs());
+
+  std::vector<std::string> languages;
+  translate_prefs->GetLanguageList(&languages);
 
-LanguageSettingsPrivateSetLanguageListFunction::
-    ~LanguageSettingsPrivateSetLanguageListFunction() {
+  if (std::find(languages.begin(), languages.end(), language_code) !=
+      languages.end()) {
+    LOG(ERROR) << "Language " << language_code << " already enabled";
+    return RespondNow(NoArguments());
+  }
+
+  languages.push_back(parameters->language_code);
+  translate_prefs->UpdateLanguageList(languages);
+
+  return RespondNow(NoArguments());
 }
 
+LanguageSettingsPrivateDisableLanguageFunction::
+    LanguageSettingsPrivateDisableLanguageFunction()
+    : chrome_details_(this) {}
+
+LanguageSettingsPrivateDisableLanguageFunction::
+    ~LanguageSettingsPrivateDisableLanguageFunction() {}
+
 ExtensionFunction::ResponseAction
-LanguageSettingsPrivateSetLanguageListFunction::Run() {
-  std::unique_ptr<language_settings_private::SetLanguageList::Params>
+LanguageSettingsPrivateDisableLanguageFunction::Run() {
+  std::unique_ptr<language_settings_private::DisableLanguage::Params>
       parameters =
-          language_settings_private::SetLanguageList::Params::Create(*args_);
+          language_settings_private::DisableLanguage::Params::Create(*args_);
   EXTENSION_FUNCTION_VALIDATE(parameters.get());
+  const std::string& language_code = parameters->language_code;
 
   std::unique_ptr<translate::TranslatePrefs> translate_prefs =
       ChromeTranslateClient::CreateTranslatePrefs(
           chrome_details_.GetProfile()->GetPrefs());
-  translate_prefs->UpdateLanguageList(parameters->language_codes);
+
+  std::vector<std::string> languages;
+  translate_prefs->GetLanguageList(&languages);
+
+  auto it = std::find(languages.begin(), languages.end(), language_code);
+  if (it == languages.end()) {
+    LOG(ERROR) << "Language " << language_code << " not enabled";
+    return RespondNow(NoArguments());
+  }
+
+  languages.erase(it);
+  translate_prefs->UpdateLanguageList(languages);
 
   return RespondNow(NoArguments());
 }