DevTools: Remove unused variables. Disallow unused variables with eslint

third_party/WebKit/Source/devtools/front_end/sources/TabbedEditorContainer.js

 /*
  * Copyright (C) 2011 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:
  *
  * 1. Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *
@@ skipping 280 matching lines @@
    * @param {string} id
    * @param {string} nextTabId
    */
   _maybeCloseTab(id, nextTabId) {
     var uiSourceCode = this._files[id];
     var shouldPrompt = uiSourceCode.isDirty() && uiSourceCode.project().canSetFileContent();
     // FIXME: this should be replaced with common Save/Discard/Cancel dialog.
     if (!shouldPrompt ||
         confirm(Common.UIString('Are you sure you want to close unsaved file: %s?', uiSourceCode.name()))) {
       uiSourceCode.resetWorkingCopy();
-      var previousView = this._currentView;
       if (nextTabId)
         this._tabbedPane.selectTab(nextTabId, true);
       this._tabbedPane.closeTab(id, true);
       return true;
     }
     return false;
   }
 
   /**
    * @param {!Array.<string>} ids
@@ skipping 491 matching lines @@
 
   /**
    * @override
    * @param {string} tabId
    * @param {!UI.ContextMenu} contextMenu
    */
   onContextMenu(tabId, contextMenu) {
     this._editorContainer._onContextMenu(tabId, contextMenu);
   }
 };