DevTools: Decouple shortcuts from actions, introduce shortcut contexts

Source/devtools/front_end/TabbedPane.js

 /*
  * Copyright (C) 2010 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 40 matching lines @@
     this._dropDownButton = this._createDropDownButton();
 }
 
 WebInspector.TabbedPane.EventTypes = {
     TabSelected: "TabSelected",
     TabClosed: "TabClosed"
 }
 
 WebInspector.TabbedPane.prototype = {
     /**
-     * @return {!WebInspector.View}
+     * @return {?WebInspector.View}
      */
     get visibleView()
     {
         return this._currentTab ? this._currentTab.view : null;
     },
 
     /**
      * @return {!Array.<!WebInspector.View>}
      */
     tabViews: function()
     {
         /**
          * @param {!WebInspector.TabbedPaneTab} tab
          * @return {!WebInspector.View}
          */
         function tabToView(tab)
         {
             return tab.view;
         }
         return this._tabs.map(tabToView);
     },
 
     /**
-     * @return {string}
+     * @return {?string}
      */
     get selectedTabId()
     {
         return this._currentTab ? this._currentTab.id : null;
     },
 
     /**
      * @type {boolean} shrinkableTabs
      */
     set shrinkableTabs(shrinkableTabs)
@@ skipping 1041 matching lines @@
         if (setting.get())
             this._tabbedPane.appendTab(id, title, new WebInspector.View());
     },
 
     /**
      * @param {!WebInspector.Event} event
      */
     _tabSelected: function(event)
     {
         var tabId = this._tabbedPane.selectedTabId;
+        if (!tabId)
+            return;
         var view = this._viewForId(tabId);
         if (view)
             this._tabbedPane.changeTabView(tabId, view);
     },
 
     /**
      * @return {?WebInspector.View}
      */
     _viewForId: function(id)
     {
         if (this._views.contains(id))
             return /** @type {!WebInspector.View} */ (this._views.get(id));
         var view = this._extensions[id] ? /** @type {!WebInspector.View} */ (this._extensions[id].instance()) : null;
         this._views.put(id, view);
         if (this._viewCallback && view)
             this._viewCallback(id, view);
         return view;
     }
 }