DevTools: make extension server a part of core, panels' code should depend on it.

LayoutTests/inspector/extensions/extensions-sidebar.html

Index: LayoutTests/inspector/extensions/extensions-sidebar.html
diff --git a/LayoutTests/inspector/extensions/extensions-sidebar.html b/LayoutTests/inspector/extensions/extensions-sidebar.html
index f8a734272a619bd3fb69d480f7a4625088102840..86716953ec5b3b4f599a4cac9d578949afbe2506 100644
--- a/LayoutTests/inspector/extensions/extensions-sidebar.html
+++ b/LayoutTests/inspector/extensions/extensions-sidebar.html
@@ -26,8 +26,13 @@ function initialize_extensionsSidebarTest()
 
     InspectorTest._extensionSidebar = function(panelName)
     {
-        var sidebarPanes = WebInspector.panels[panelName]._extensionSidebarPanes;
-        return sidebarPanes[sidebarPanes.length - 1];
+        var sidebarPanes = WebInspector.extensionServer.sidebarPanes();
+        var result;
+        for (var i = 0; i < sidebarPanes.length; ++i) {
+            if (sidebarPanes[i].panelName() === panelName)
+                result = sidebarPanes[i];
+        }
+        return result;
     }
 }