DevTools: Decouple shortcuts from actions, introduce shortcut contexts

Source/devtools/front_end/Drawer.js

Index: Source/devtools/front_end/Drawer.js
diff --git a/Source/devtools/front_end/Drawer.js b/Source/devtools/front_end/Drawer.js
index e13a25473cc26378b20776e0a53445d64713fb05..698763742e850bff671552d28d76a33ad8a4c8af 100644
--- a/Source/devtools/front_end/Drawer.js
+++ b/Source/devtools/front_end/Drawer.js
@@ -160,7 +160,7 @@ WebInspector.Drawer.prototype = {
     },
 
     /**
-     * @return {!WebInspector.View} view
+     * @return {?WebInspector.View} view
      */
     _visibleView: function()
     {
@@ -173,7 +173,7 @@ WebInspector.Drawer.prototype = {
     _tabSelected: function(event)
     {
         var tabId = this._tabbedPane.selectedTabId;
-        if (event.data["isUserGesture"] && !this._tabbedPane.isTabCloseable(tabId))
+        if (tabId && event.data["isUserGesture"] && !this._tabbedPane.isTabCloseable(tabId))
             this._lastSelectedViewSetting.set(tabId);
     },
 
@@ -194,7 +194,7 @@ WebInspector.Drawer.prototype = {
     },
 
     /**
-     * @return {string}
+     * @return {?string}
      */
     selectedViewId: function()
     {