DevTools: Decouple shortcuts from actions, introduce shortcut contexts

Source/devtools/front_end/TabbedPane.js

Index: Source/devtools/front_end/TabbedPane.js
diff --git a/Source/devtools/front_end/TabbedPane.js b/Source/devtools/front_end/TabbedPane.js
index 6b2ebf2c4ac63bd6531169ff235d4e1497f18720..5c29a3db73f8130c89e359927f1fd9784e794036 100644
--- a/Source/devtools/front_end/TabbedPane.js
+++ b/Source/devtools/front_end/TabbedPane.js
@@ -58,7 +58,7 @@ WebInspector.TabbedPane.EventTypes = {
 
 WebInspector.TabbedPane.prototype = {
     /**
-     * @return {!WebInspector.View}
+     * @return {?WebInspector.View}
      */
     get visibleView()
     {
@@ -82,7 +82,7 @@ WebInspector.TabbedPane.prototype = {
     },
 
     /**
-     * @return {string}
+     * @return {?string}
      */
     get selectedTabId()
     {
@@ -1144,6 +1144,8 @@ WebInspector.ExtensibleTabbedPaneController.prototype = {
     _tabSelected: function(event)
     {
         var tabId = this._tabbedPane.selectedTabId;
+        if (!tabId)
+            return;
         var view = this._viewForId(tabId);
         if (view)
             this._tabbedPane.changeTabView(tabId, view);