DevTools: nuke LocalStorage settings once again when upgrading from settings v12 to v13

Source/devtools/front_end/common/Settings.js

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 547 matching lines @@
             device["show"] = "Default";
             newList.push(device);
         }
         if (newList.length)
             WebInspector.settings.createSetting(newSettingName, []).set(newList);
         oldSetting.remove();
     },
 
     _updateVersionFrom11To12: function()
     {
+        this._migrateSettingsFromLocalStorage();

[pfeldman, 2015/06/23 13:58:02]

We can't modify things in the past, assume users are already on v12.

[alph, 2015/06/23 14:11:36]

you probably took it offline, but could you please excuse my curiosity, what's
the point of doing it twice for users migrating from 11 to 13?

+    },
+
+    _updateVersionFrom12To13: function()
+    {
+        this._migrateSettingsFromLocalStorage();

[pfeldman, 2015/06/23 13:58:03]

You should not migrate more than once. Should we just nuke the version off
localStorage?

+        WebInspector.settings.createSetting("timelineOverviewMode", "").remove();
+    },
+
+    _migrateSettingsFromLocalStorage: function()
+    {
         // This step migrates all the settings except for the ones below into the browser profile.
         var localSettings = [ "advancedSearchConfig", "breakpoints", "consoleHistory", "domBreakpoints", "eventListenerBreakpoints",
                               "fileSystemMapping", "lastSelectedSourcesSidebarPaneTab", "previouslyViewedFiles",
                               "savedURLs", "watchExpressions", "workspaceExcludedFolders", "xhrBreakpoints" ].keySet();
         if (!window.localStorage)
             return;
 
         for (var key in window.localStorage) {
             if (key in localSettings)
                 continue;
             var value = window.localStorage[key];
             window.localStorage.removeItem(key);
             WebInspector.settings._settingsStorage[key] = value;
         }
     },
 
-    _updateVersionFrom12To13: function()
-    {
-        WebInspector.settings.createSetting("timelineOverviewMode", "").remove();
-    },
-
     /**
      * @param {!WebInspector.Setting} breakpointsSetting
      * @param {number} maxBreakpointsCount
      */
     _clearBreakpointsWhenTooMany: function(breakpointsSetting, maxBreakpointsCount)
     {
         // If there are too many breakpoints in a storage, it is likely due to a recent bug that caused
         // periodical breakpoints duplication leading to inspector slowness.
         if (breakpointsSetting.get().length > maxBreakpointsCount)
             breakpointsSetting.set([]);
@@ skipping 15 matching lines @@
 }
 
 /**
  * @param {string} settingName
  * @return {!WebInspector.Setting}
  */
 WebInspector.settingForTest = function(settingName)
 {
     return WebInspector.settings.settingForTest(settingName);
 }