[Devtools] Cleanup DataGrid's typecast and identifier naming

third_party/WebKit/Source/devtools/front_end/resources/ServiceWorkerCacheViews.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @constructor
  * @extends {WebInspector.SimpleView}
  * @param {!WebInspector.ServiceWorkerCacheModel} model
  * @param {!WebInspector.ServiceWorkerCacheModel.Cache} cache
  */
@@ skipping 18 matching lines @@
     this.update(cache);
     this._entries = [];
 };
 
 WebInspector.ServiceWorkerCacheView.prototype = {
     /**
      * @return {!WebInspector.DataGrid}
      */
     _createDataGrid: function()
     {
-        var columns = [];
-        columns.push({id: "number", title: WebInspector.UIString("#"), width: "50px"});
-        columns.push({id: "request", title: WebInspector.UIString("Request")});
-        columns.push({id: "response", title: WebInspector.UIString("Response")});
-
-        var dataGrid = new WebInspector.DataGrid(columns, undefined, this._deleteButtonClicked.bind(this), this._updateData.bind(this, true));
-        return dataGrid;
+        var columns = /** @type {!Array<!WebInspector.DataGrid.ColumnDescriptor>} */ ([
+            {id: "number", title: WebInspector.UIString("#"), width: "50px"},
+            {id: "request", title: WebInspector.UIString("Request")},
+            {id: "response", title: WebInspector.UIString("Response")}
+        ]);
+        return new WebInspector.DataGrid(columns, undefined, this._deleteButtonClicked.bind(this), this._updateData.bind(this, true));
     },
 
     _createEditorToolbar: function()
     {
         var editorToolbar = new WebInspector.Toolbar("data-view-toolbar", this.element);
 
         this._pageBackButton = new WebInspector.ToolbarButton(WebInspector.UIString("Show previous page"), "play-backwards-toolbar-item");
         this._pageBackButton.addEventListener("click", this._pageBackButtonClicked, this);
         editorToolbar.appendToolbarItem(this._pageBackButton);
 
@@ skipping 98 matching lines @@
     },
 
     clear: function()
     {
         this._dataGrid.rootNode().removeChildren();
         this._entries = [];
     },
 
     __proto__: WebInspector.SimpleView.prototype
 };