Reland of [DevTools] Show icon in top toolbar when Node target is available

third_party/WebKit/Source/devtools/front_end/main/Main.js

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2007 Matt Lilek (pewtermoose@gmail.com).
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
@@ skipping 710 matching lines @@
         continue;
       moreTools.appendItem(extension.title(), UI.viewManager.showView.bind(UI.viewManager, descriptor['id']));
     }
 
     var helpSubMenu = contextMenu.namedSubMenu('mainMenuHelp');
     helpSubMenu.appendAction('settings.documentation');
     helpSubMenu.appendItem('Release Notes', () => InspectorFrontendHost.openInNewTab(Help.latestReleaseNote().link));
   }
 };
 
+/**
+ * @implements {UI.ToolbarItem.Provider}
+ */
+Main.Main.NodeIndicator = class {
+  constructor() {
+    var element = createElement('div');
+    var shadowRoot = UI.createShadowRootWithCoreStyles(element, 'main/nodeIcon.css');
+    this._element = shadowRoot.createChild('div', 'node-icon');
+    element.addEventListener('click', () => InspectorFrontendHost.openNodeFrontend(), false);
+    this._button = new UI.ToolbarItem(element);
+    this._button.setTitle(Common.UIString('Open dedicated DevTools for Node.js'));
+    SDK.targetManager.addEventListener(SDK.TargetManager.Events.AvailableNodeTargetsChanged, this._update, this);
+    this._button.setVisible(false);
+    this._update();
+  }
+
+  _update() {
+    this._element.classList.toggle('inactive', !SDK.targetManager.availableNodeTargetsCount());
+    if (SDK.targetManager.availableNodeTargetsCount())
+      this._button.setVisible(true);
+  }
+
+  /**
+   * @override
+   * @return {?UI.ToolbarItem}
+   */
+  item() {
+    return this._button;
+  }
+};
+
 Main.NetworkPanelIndicator = class {
   constructor() {
     // TODO: we should not access network from other modules.
     if (!UI.inspectorView.hasPanel('network'))
       return;
     var manager = SDK.multitargetNetworkManager;
     manager.addEventListener(SDK.MultitargetNetworkManager.Events.ConditionsChanged, updateVisibility);
     manager.addEventListener(SDK.MultitargetNetworkManager.Events.BlockedPatternsChanged, updateVisibility);
     updateVisibility();
 
@@ skipping 211 matching lines @@
    * @override
    * @return {?Element}
    */
   settingElement() {
     return UI.SettingsUI.createSettingCheckbox(
         Common.UIString('Show rulers'), Common.moduleSetting('showMetricsRulers'));
   }
 };
 
 new Main.Main();