DevTools: initialize "format script" button with current UISourceCode

Source/devtools/front_end/sources/ScriptFormatterEditorAction.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
  * @implements {WebInspector.DebuggerSourceMapping}
  * @param {!WebInspector.Target} target
  * @param {!WebInspector.ScriptFormatterEditorAction} editorAction
  */
@@ skipping 213 matching lines @@
         if (this._button)
             return this._button.element;
 
         this._sourcesView = sourcesView;
         this._sourcesView.addEventListener(WebInspector.SourcesView.Events.EditorSelected, this._editorSelected.bind(this));
         this._sourcesView.addEventListener(WebInspector.SourcesView.Events.EditorClosed, this._editorClosed.bind(this));
 
         this._button = new WebInspector.StatusBarButton(WebInspector.UIString("Pretty print"), "sources-toggle-pretty-print-status-bar-item");
         this._button.toggled = false;
         this._button.addEventListener("click", this._toggleFormatScriptSource, this);
-        this._updateButton(null);
+        this._updateButton(sourcesView.currentUISourceCode());
 
         return this._button.element;
     },
 
     /**
      * @param {?WebInspector.UISourceCode} uiSourceCode
      * @return {boolean}
      */
     _isFormatableScript: function(uiSourceCode)
     {
@@ skipping 182 matching lines @@
 
             var targets = WebInspector.targetManager.targets();
             for (var i = 0; i < targets.length; ++i) {
                 var scriptMapping = /** @type {!WebInspector.FormatterScriptMapping} */(this._scriptMappingByTarget.get(targets[i]));
                 WebInspector.debuggerWorkspaceBinding.setSourceMapping(targets[i], formattedUISourceCode, scriptMapping);
             }
             this._showIfNeeded(uiSourceCode, formattedUISourceCode, formatterMapping);
         }
     }
 }