DevTools: TabbedLocations only materialize tabs when needed

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

Index: third_party/WebKit/Source/devtools/front_end/ui/TabbedPane.js
diff --git a/third_party/WebKit/Source/devtools/front_end/ui/TabbedPane.js b/third_party/WebKit/Source/devtools/front_end/ui/TabbedPane.js
index 64313e21f74f2f3aeee400765ba48a39bc011b4a..2d4390c0389e2f253b558876dec22d2236486c5b 100644
--- a/third_party/WebKit/Source/devtools/front_end/ui/TabbedPane.js
+++ b/third_party/WebKit/Source/devtools/front_end/ui/TabbedPane.js
@@ -440,6 +440,7 @@ UI.TabbedPane = class extends UI.VBox {
     var effectiveTab = this._currentTab || this._tabsHistory[0];
     if (effectiveTab && this._autoSelectFirstItemOnShow)
       this.selectTab(effectiveTab.id);
+    this.dispatchEventToListeners(UI.TabbedPane.Events.TabsShown, this._currentTab);
   }
 
   /**
@@ -831,7 +832,8 @@ UI.TabbedPane = class extends UI.VBox {
 UI.TabbedPane.Events = {
   TabSelected: Symbol('TabSelected'),
   TabClosed: Symbol('TabClosed'),
-  TabOrderChanged: Symbol('TabOrderChanged')
+  TabOrderChanged: Symbol('TabOrderChanged'),
+  TabsShown: Symbol('TabsShown')
 };
 
 /**