DevTools: fix author shadow dom inspection mode, speacial-case ua. Fix crash from the bug.

Source/devtools/front_end/SettingsScreen.js

 /*
  * Copyright (C) 2013 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 284 matching lines @@
 
     p = this._appendSection(WebInspector.UIString("Elements"));
     var colorFormatElement = this._createSelectSetting(WebInspector.UIString("Color format"), [
             [ WebInspector.UIString("As authored"), WebInspector.Color.Format.Original ],
             [ "HEX: #DAC0DE", WebInspector.Color.Format.HEX ],
             [ "RGB: rgb(128, 255, 255)", WebInspector.Color.Format.RGB ],
             [ "HSL: hsl(300, 80%, 90%)", WebInspector.Color.Format.HSL ]
         ], WebInspector.settings.colorFormat);
     p.appendChild(colorFormatElement);
     p.appendChild(WebInspector.SettingsUI.createSettingCheckbox(WebInspector.UIString("Show user agent styles"), WebInspector.settings.showUserAgentStyles));
-    p.appendChild(WebInspector.SettingsUI.createSettingCheckbox(WebInspector.UIString("Show user agent shadow DOM"), WebInspector.settings.showShadowDOM));
+    p.appendChild(WebInspector.SettingsUI.createSettingCheckbox(WebInspector.UIString("Show user agent shadow DOM"), WebInspector.settings.showUAShadowDOM));
     p.appendChild(WebInspector.SettingsUI.createSettingCheckbox(WebInspector.UIString("Word wrap"), WebInspector.settings.domWordWrap));
     p.appendChild(WebInspector.SettingsUI.createSettingCheckbox(WebInspector.UIString("Show rulers"), WebInspector.settings.showMetricsRulers));
 
     p = this._appendSection(WebInspector.UIString("Sources"));
     p.appendChild(WebInspector.SettingsUI.createSettingCheckbox(WebInspector.UIString("Search in content scripts"), WebInspector.settings.searchInContentScripts));
     p.appendChild(WebInspector.SettingsUI.createSettingCheckbox(WebInspector.UIString("Enable JavaScript source maps"), WebInspector.settings.jsSourceMapsEnabled));
 
     var checkbox = WebInspector.SettingsUI.createSettingCheckbox(WebInspector.UIString("Enable CSS source maps"), WebInspector.settings.cssSourceMapsEnabled);
     p.appendChild(checkbox);
     var fieldset = WebInspector.SettingsUI.createSettingFieldset(WebInspector.settings.cssSourceMapsEnabled);
@@ skipping 790 matching lines @@
             var inputElement = this._addInputElements[columnId];
             inputElement.value = "";
         }
     },
 
     __proto__: WebInspector.SettingsList.prototype
 }
 
 /** @type {!WebInspector.SettingsController} */
 WebInspector.settingsController;