MD Settings: add a semi-functional System page

chrome/browser/extensions/api/settings_private/prefs_util.h

 // Copyright 2015 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_EXTENSIONS_API_SETTINGS_PRIVATE_PREFS_UTIL_H_
 #define CHROME_BROWSER_EXTENSIONS_API_SETTINGS_PRIVATE_PREFS_UTIL_H_
 
 #include <map>
 #include <string>
 
@@ skipping 12 matching lines @@
  public:
   // Success or error statuses from calling SetPref.
   enum SetPrefResult {
     SUCCESS,
     PREF_NOT_MODIFIABLE,
     PREF_NOT_FOUND,
     PREF_TYPE_MISMATCH,
     PREF_TYPE_UNSUPPORTED
   };
 
+  // TODO(dbeam): why is the key a std::string rather than const char*?
   using TypedPrefMap = std::map<std::string, api::settings_private::PrefType>;
 
   explicit PrefsUtil(Profile* profile);
   virtual ~PrefsUtil();
 
   // Gets the list of whitelisted pref keys -- that is, those which correspond
   // to prefs that clients of the settingsPrivate API may retrieve and
   // manipulate.
   const TypedPrefMap& GetWhitelistedKeys();
 
@@ skipping 57 matching lines @@
 
   SetPrefResult SetCrosSettingsPref(const std::string& name,
                                     const base::Value* value);
 
   Profile* profile_;  // weak
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_SETTINGS_PRIVATE_PREFS_UTIL_H_