Add model listeners in the Security panel constructor (instead of in targetAdded).

Source/devtools/front_end/security/SecurityPanel.js

 // Copyright 2015 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
  * @extends {WebInspector.PanelWithSidebar}
  * @implements {WebInspector.TargetManager.Observer}
  */
 WebInspector.SecurityPanel = function()
@@ skipping 16 matching lines @@
     this._sidebarOriginSection = new WebInspector.SidebarSectionTreeElement(WebInspector.UIString("Origins"));
     this._sidebarOriginSection.listItemElement.classList.add("security-sidebar-origins");
     sidebarTree.appendChild(this._sidebarOriginSection);
 
     this._mainView = new WebInspector.SecurityMainView();
 
     /** @type {!Map<!WebInspector.SecurityPanel.Origin, !WebInspector.SecurityPanel.OriginState>} */
     this._origins = new Map();
     // TODO(lgarron): add event listeners to call _clear() once we figure out how to clear the panel properly (https://crbug.com/522762).
 
+    WebInspector.targetManager.addModelListener(WebInspector.NetworkManager, WebInspector.NetworkManager.EventTypes.ResponseReceivedSecurityDetails, this._onResponseReceivedSecurityDetails, this);
+    WebInspector.targetManager.addModelListener(WebInspector.SecurityModel, WebInspector.SecurityModel.EventTypes.SecurityStateChanged, this._onSecurityStateChanged, this);
+
     WebInspector.targetManager.observeTargets(this);
 }
 
 /** @typedef {string} */
 WebInspector.SecurityPanel.Origin;
 
 /**
  * @typedef {Object}
  * @property {!SecurityAgent.SecurityState} securityState - Current security state of the origin.
  * @property {?NetworkAgent.SecurityDetails} securityDetails - Security details of the origin, if available.
@@ skipping 110 matching lines @@
         var ordering = ["unknown", "insecure", "neutral", "warning", "secure"];
         return (ordering.indexOf(stateA) < ordering.indexOf(stateB)) ? stateA : stateB;
     },
 
     /**
      * @override
      * @param {!WebInspector.Target} target
      */
     targetAdded: function(target)
     {
-        if (!this._target) {
-            this._target = target;
-            this._securityModel = WebInspector.SecurityModel.fromTarget(target);
-            this._securityModel.addEventListener(WebInspector.SecurityModel.EventTypes.SecurityStateChanged, this._onSecurityStateChanged, this);
-            this._updateSecurityState(this._securityModel.securityState(), []);
-
-            this._origins.clear();
-            this._networkManager = target.networkManager;
-            this._networkManager.addEventListener(WebInspector.NetworkManager.EventTypes.ResponseReceivedSecurityDetails, this._onResponseReceivedSecurityDetails, this);
-        }
+        WebInspector.SecurityModel.fromTarget(target);
     },
 
     /**
      * @override
      * @param {!WebInspector.Target} target
      */
     targetRemoved: function(target)
     {
-        if (target === this._target) {
-            this._securityModel.removeEventListener(WebInspector.SecurityModel.EventTypes.SecurityStateChanged, this._onSecurityStateChanged, this);
-            delete this._securityModel;
-            this._networkManager.removeEventListener(WebInspector.NetworkManager.EventTypes.ResponseReceivedSecurityDetails, this._onResponseReceivedSecurityDetails, this);
-            delete this._networkManager;
-            delete this._target;
-            this._clear();
-        }
     },
 
     _clear: function()
     {
         this._updateSecurityState(SecurityAgent.SecurityState.Unknown, []);
         this._sidebarMainViewElement.select();
         this._sidebarOriginSection.removeChildren();
         this._origins.clear();
     },
 
@@ skipping 323 matching lines @@
 
         var valueDiv = row.createChild("div");
         if (value instanceof HTMLDivElement) {
             valueDiv.appendChild(value);
         } else {
             valueDiv.textContent = value;
         }
     }
 }