DevTools: Implement extension-based status bar buttons

Source/devtools/front_end/ui/StatusBarButton.js

 /*
  * Copyright (C) 2009 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 416 matching lines @@
                     break;
                 }
             }
         }
     },
 
     __proto__: WebInspector.StatusBarItem.prototype
 }
 
 /**
+ * @interface
+ */
+WebInspector.StatusBarButton.Provider = function()
+{
+}
+
+WebInspector.StatusBarButton.Provider.prototype = {
+    /**
+     * @return {?WebInspector.StatusBarButton}
+     */
+    button: function() {}
+}
+
+/**
  * @constructor
  * @extends {WebInspector.StatusBarItem}
  * @param {?function(!Event)} changeHandler
  * @param {string=} className
  */
 WebInspector.StatusBarComboBox = function(changeHandler, className)
 {
     WebInspector.StatusBarItem.call(this, "span");
     this.element.className = "status-bar-select-container";
 
@@ skipping 228 matching lines @@
         var options = [];
         for (var index = 0; index < this._states.length; index++) {
             if (this._states[index] !== this.state && this._states[index] !== this._currentState)
                 options.push(this._buttons[index]);
         }
         return options;
     },
 
     __proto__: WebInspector.StatusBarButton.prototype
 }