DevTools: Remove unused variables. Disallow unused variables with eslint

third_party/WebKit/Source/devtools/front_end/elements/ElementsTreeElement.js

 /*
  * Copyright (C) 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2008 Matt Lilek <webkit@mattlilek.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 460 matching lines @@
   }
 
   populateTextContextMenu(contextMenu, textNode) {
     if (!this._editing)
       contextMenu.appendItem(Common.UIString.capitalize('Edit ^text'), this._startEditingTextNode.bind(this, textNode));
     this.populateNodeContextMenu(contextMenu);
   }
 
   populateNodeContextMenu(contextMenu) {
     // Add free-form node-related actions.
-    var openTagElement = this._node[this.treeOutline.treeElementSymbol()] || this;
     var isEditable = this.hasEditableNode();
     if (isEditable && !this._editing)
       contextMenu.appendItem(Common.UIString('Edit as HTML'), this._editAsHTML.bind(this));
     var isShadowRoot = this._node.isShadowRoot();
 
     // Place it here so that all "Copy"-ing items stick together.
     var copyMenu = contextMenu.appendSubMenuItem(Common.UIString('Copy'));
     var createShortcut = UI.KeyboardShortcut.shortcutToString;
     var modifier = UI.KeyboardShortcut.Modifiers.CtrlOrMeta;
     var treeOutline = this.treeOutline;
@@ skipping 1072 matching lines @@
 
 // A union of HTML4 and HTML5-Draft elements that explicitly
 // or implicitly (for HTML5) forbid the closing tag.
 Elements.ElementsTreeElement.ForbiddenClosingTagElements = new Set([
   'area', 'base',  'basefont', 'br',   'canvas',   'col',  'command', 'embed',  'frame', 'hr',
   'img',  'input', 'keygen',   'link', 'menuitem', 'meta', 'param',   'source', 'track', 'wbr'
 ]);
 
 // These tags we do not allow editing their tag name.
 Elements.ElementsTreeElement.EditTagBlacklist = new Set(['html', 'head', 'body']);