Settings reset prompt: Fetch default settings only when needed.

chrome/browser/safe_browsing/settings_reset_prompt/default_settings_fetcher.h

 // Copyright 2017 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.
 
 #ifndef CHROME_BROWSER_SAFE_BROWSING_SETTINGS_RESET_PROMPT_DEFAULT_SETTINGS_FETCHER_H_
 #define CHROME_BROWSER_SAFE_BROWSING_SETTINGS_RESET_PROMPT_DEFAULT_SETTINGS_FETCHER_H_
 
 #include <memory>
 
 #include "base/callback.h"
 
 class BrandcodedDefaultSettings;
 class BrandcodeConfigFetcher;
 
 namespace safe_browsing {
 
 // Class that fetches default settings to be used for the settings reset
 // prompt. The static |FetchDefaultSettings()| function will create and manage
 // the lifetime of |DefaultSettingsFetcher| instances.
 class DefaultSettingsFetcher {
  public:
   using SettingsCallback =
       base::Callback<void(std::unique_ptr<BrandcodedDefaultSettings>)>;
 
   // Fetches default settings and passes the corresponding
   // |BrandcodedDefaultSettings| object to |callback| on the UI thread. This
   // function must be called on the UI thread as well.
+  //
+  // If fetching of default settings on the network fails, a default-constructed
+  // BrandcodedDefaultSettings object will be passed to |callback|.
   static void FetchDefaultSettings(SettingsCallback callback);
   // Allows tests to specify the default settings that were fetched in
   // |fetched_settings|. Passing nullptr as |fetched_settings| corresponds to
   // the case when fetching default settings over the network fails.
   static void FetchDefaultSettingsForTesting(
       SettingsCallback callback,
       std::unique_ptr<BrandcodedDefaultSettings> fetched_settings);
 
  private:
   // Instances of |DefaultSettingsFetcher| own themselves and will delete
@@ skipping 17 matching lines @@
   void PostCallbackAndDeleteSelf(
       std::unique_ptr<BrandcodedDefaultSettings> default_settings);
 
   std::unique_ptr<BrandcodeConfigFetcher> config_fetcher_;
   SettingsCallback callback_;
 };
 
 }  // namespace safe_browsing
 
 #endif  // CHROME_BROWSER_SAFE_BROWSING_SETTINGS_RESET_PROMPT_DEFAULT_SETTINGS_FETCHER_H_