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 5d344f106ad837495a909f1493aec62e04796378..a3d8922a6568e52812b629fad2e793f6f6d4a5be 100644
--- a/Source/devtools/front_end/TabbedPane.js
+++ b/Source/devtools/front_end/TabbedPane.js
@@ -54,7 +54,7 @@ WebInspector.TabbedPane.EventTypes = {
 
 WebInspector.TabbedPane.prototype = {
     /**
-     * @return {!WebInspector.View}
+     * @return {?WebInspector.View}
      */
     get visibleView()
     {
@@ -62,7 +62,7 @@ WebInspector.TabbedPane.prototype = {
     },
 
     /**
-     * @return {string}
+     * @return {?string}
      */
     get selectedTabId()
     {
@@ -1118,6 +1118,8 @@ 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);