[DevTools] Make toolbar counters declarative.

Source/devtools/front_end/main/App.js

Index: Source/devtools/front_end/main/App.js
diff --git a/Source/devtools/front_end/main/App.js b/Source/devtools/front_end/main/App.js
index ed9a8987cc0965318d886aa3acbc023b3214d970..dc3076990b21eede0f64d00858887f2cd57835e8 100644
--- a/Source/devtools/front_end/main/App.js
+++ b/Source/devtools/front_end/main/App.js
@@ -65,7 +65,7 @@ WebInspector.App.prototype = {
 
 /**
  * @constructor
- * @implements {WebInspector.StatusBarButton.Provider}
+ * @implements {WebInspector.StatusBarItem.Provider}
  */
 WebInspector.App.EmulationButtonProvider = function()
 {
@@ -73,9 +73,9 @@ WebInspector.App.EmulationButtonProvider = function()
 
 WebInspector.App.EmulationButtonProvider.prototype = {
     /**
-     * @return {?WebInspector.StatusBarButton}
+     * @return {?WebInspector.StatusBarItem}
      */
-    button: function()
+    item: function()
     {
         if (!(WebInspector.app instanceof WebInspector.App))
             return null;