DevTools: use target-based model accessors only.

Source/devtools/front_end/timeline/CountersGraph.js

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 56 matching lines @@
     // Populate sidebar
     this._infoView = new WebInspector.VBox();
     this._infoView.element.classList.add("sidebar-tree");
     this._infoView.element.createChild("div", "sidebar-tree-section").textContent = title;
     this.setSidebarView(this._infoView);
     this._counters = [];
     this._counterUI = [];
 }
 
 WebInspector.CountersGraph.prototype = {
+    /**
+     * @return {?WebInspector.Target}
+     */
+    target: function()
+    {
+        return this._model.target();
+    },
+
     _createCurrentValuesBar: function()
     {
         this._currentValuesBar = this._graphsContainer.element.createChild("div");
         this._currentValuesBar.id = "counter-values-bar";
     },
 
     /**
      * @param {string} uiName
      * @param {string} uiValueTemplate
      * @param {string} color
@@ skipping 486 matching lines @@
     },
 
     _toggleCheckbox: function(event)
     {
         this.checked = !this.checked;
         this.dispatchEventToListeners(WebInspector.SwatchCheckbox.Events.Changed);
     },
 
     __proto__: WebInspector.Object.prototype
 }