[DevTools] Rework some focus code.

third_party/WebKit/Source/devtools/front_end/ui/Dialog.js

 /*
  * Copyright (C) 2012 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 56 matching lines @@
             WebInspector.Dialog._instance.detach();
         WebInspector.Dialog._instance = this;
 
         var document = /** @type {!Document} */ (WebInspector.Dialog._modalHostView.element.ownerDocument);
         this._disableTabIndexOnElements(document);
 
         this._glassPane = new WebInspector.GlassPane(document, this._dimmed);
         this._glassPane.element.addEventListener("click", this._onGlassPaneClick.bind(this), false);
         this.element.ownerDocument.body.addEventListener("keydown", this._keyDownBound, false);
 
-        // When a dialog closes, focus should be restored to the previous focused element when
-        // possible, otherwise the default inspector view element.
-        WebInspector.Dialog._previousFocusedElement = WebInspector.currentFocusElement();
-
         WebInspector.Widget.prototype.show.call(this, this._glassPane.element);
 
         this._position();
-        this.focus();
+        this._focusRestorer = new WebInspector.WidgetFocusRestorer(this);
     },
 
     /**
      * @override
      */
     detach: function()
     {
+        this._focusRestorer.restore();
+
         this.element.ownerDocument.body.removeEventListener("keydown", this._keyDownBound, false);
         WebInspector.Widget.prototype.detach.call(this);
 
         this._glassPane.dispose();
         delete this._glassPane;
 
-        if (WebInspector.Dialog._previousFocusedElement)
-            WebInspector.Dialog._previousFocusedElement.focus();
-        delete WebInspector.Dialog._previousFocusedElement;
-
         this._restoreTabIndexOnElements();
 
         delete WebInspector.Dialog._instance;
     },
 
     addCloseButton: function()
     {
         var closeButton = this.contentElement.createChild("div", "dialog-close-button", "dt-close-button");
         closeButton.gray = true;
         closeButton.addEventListener("click", this.detach.bind(this), false);
@@ skipping 157 matching lines @@
 {
     return WebInspector.Dialog._modalHostView;
 };
 
 WebInspector.Dialog.modalHostRepositioned = function()
 {
     if (WebInspector.Dialog._instance)
         WebInspector.Dialog._instance._position();
 };