DevTools: Remove unused variables. Disallow unused variables with eslint

third_party/WebKit/Source/devtools/front_end/sdk/SubTargetsManager.js

 // Copyright 2016 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.
 /**
  * @unrestricted
  */
 SDK.SubTargetsManager = class extends SDK.SDKModel {
   /**
    * @param {!SDK.Target} target
    */
@@ skipping 167 matching lines @@
   _createConnection(targetId, params) {
     var connection = new SDK.SubTargetConnection(this._agent, targetId, params);
     this._connections.set(targetId, connection);
     return connection;
   }
 
   /**
    * @param {string} targetId
    */
   _detachedFromTarget(targetId) {
-    var target = this._attachedTargets.get(targetId);
     this._attachedTargets.delete(targetId);
     var connection = this._connections.get(targetId);
     connection._onDisconnect.call(null, 'target terminated');
     this._connections.delete(targetId);
     this.dispatchEventToListeners(
         SDK.SubTargetsManager.Events.PendingTargetDetached, this._pendingTargets.get(targetId));
   }
 
   /**
    * @param {string} targetId
@@ skipping 253 matching lines @@
     this._attachedCallback = null;
   }
 
   /**
    * @return {boolean}
    */
   canConnect() {
     return this._isRemote;
   }
 };