--- a/security/manager/pki/resources/content/certManager.js
+++ b/security/manager/pki/resources/content/certManager.js
@@ -8,18 +8,16 @@ const { classes: Cc, interfaces: Ci, uti
 
 const nsIFilePicker = Components.interfaces.nsIFilePicker;
 const nsFilePicker = "@mozilla.org/filepicker;1";
 const nsIX509CertDB = Components.interfaces.nsIX509CertDB;
 const nsX509CertDB = "@mozilla.org/security/x509certdb;1";
 const nsIX509Cert = Components.interfaces.nsIX509Cert;
 const nsICertTree = Components.interfaces.nsICertTree;
 const nsCertTree = "@mozilla.org/security/nsCertTree;1";
-const nsIDialogParamBlock = Components.interfaces.nsIDialogParamBlock;
-const nsDialogParamBlock = "@mozilla.org/embedcomp/dialogparam;1";
 
 const gCertFileTypes = "*.p7b; *.crt; *.cert; *.cer; *.pem; *.der";
 
 var { NetUtil } = Components.utils.import("resource://gre/modules/NetUtil.jsm", {});
 var { Services } = Components.utils.import("resource://gre/modules/Services.jsm", {});
 
 var key;
 
@@ -27,20 +25,40 @@ var key;
  * List of certs currently selected in the active tab.
  * @type nsIX509Cert[]
  */
 var selected_certs = [];
 var selected_tree_items = [];
 var selected_index = [];
 var certdb;
 
+/**
+ * Cert tree for the "Authorities" tab.
+ * @type nsICertTree
+ */
 var caTreeView;
+/**
+ * Cert tree for the "Servers" tab.
+ * @type nsICertTree
+ */
 var serverTreeView;
+/**
+ * Cert tree for the "People" tab.
+ * @type nsICertTree
+ */
 var emailTreeView;
+/**
+ * Cert tree for the "Your Certificates" tab.
+ * @type nsICertTree
+ */
 var userTreeView;
+/**
+ * Cert tree for the "Other" tab.
+ * @type nsICertTree
+ */
 var orphanTreeView;
 
 var smartCardObserver = {
   observe: function() {
     onSmartCardChange();
   }
 };
 
@@ -397,77 +415,58 @@ function exportCerts()
 {
   getSelectedCerts();
 
   for (let cert of selected_certs) {
     exportToFile(window, cert);
   }
 }
 
-function deleteCerts()
-{
+/**
+ * Deletes the selected certs in the active tab.
+ */
+function deleteCerts() {
   getSelectedTreeItems();
-  var numcerts = selected_tree_items.length;
+  let numcerts = selected_tree_items.length;
   if (numcerts == 0) {
     return;
   }
 
-  var params = Components.classes[nsDialogParamBlock].createInstance(nsIDialogParamBlock);
-
-  var selTab = document.getElementById('certMgrTabbox').selectedItem;
-  var selTabID = selTab.getAttribute('id');
+  const treeViewMap = {
+    "mine_tab": userTreeView,
+    "websites_tab": serverTreeView,
+    "ca_tab": caTreeView,
+    "others_tab": emailTreeView,
+    "orphan_tab": orphanTreeView,
+  };
+  let selTab = document.getElementById("certMgrTabbox").selectedItem;
+  let selTabID = selTab.getAttribute("id");
 
-  switch (selTabID) {
-    case "mine_tab":
-    case "websites_tab":
-    case "ca_tab":
-    case "others_tab":
-    case "orphan_tab":
-      params.SetString(0, selTabID);
-      break;
-    default:
-      return;
+  if (!(selTabID in treeViewMap)) {
+    return;
   }
 
-  let array = Cc["@mozilla.org/array;1"].createInstance(Ci.nsIMutableArray);
-  for (let treeItem of selected_tree_items) {
-    array.appendElement(treeItem, false);
-  }
-  params.objects = array;
-
-  window.openDialog('chrome://pippki/content/deletecert.xul', "",
-                    'chrome,centerscreen,modal', params);
-
-  if (params.GetInt(1) == 1) {
-    // user closed dialog with OK
-    var treeView = null;
-    var loadParam = null;
+  let retVals = {
+    deleteConfirmed: false,
+  };
+  window.openDialog("chrome://pippki/content/deletecert.xul", "",
+                    "chrome,centerscreen,modal", selTabID, selected_tree_items,
+                    retVals);
 
-    selTab = document.getElementById('certMgrTabbox').selectedItem;
-    selTabID = selTab.getAttribute('id');
-    if (selTabID == 'mine_tab') {
-      treeView = userTreeView;
-    } else if (selTabID == "others_tab") {
-      treeView = emailTreeView;
-    } else if (selTabID == "websites_tab") {
-      treeView = serverTreeView;
-    } else if (selTabID == "ca_tab") {
-      treeView = caTreeView;
-    } else if (selTabID == "orphan_tab") {
-      treeView = orphanTreeView;
-    }
+  if (retVals.deleteConfirmed) {
+    let treeView = treeViewMap[selTabID];
 
     for (let t = numcerts - 1; t >= 0; t--) {
       treeView.deleteEntryObject(selected_index[t]);
     }
 
     selected_tree_items = [];
     selected_index = [];
     treeView.selection.clearSelection();
-    if (selTabID == 'mine_tab') {
+    if (selTabID == "mine_tab") {
       enableBackupAllButton();
     }
   }
 }
 
 function viewCerts()
 {
   getSelectedCerts();

--- a/security/manager/pki/resources/content/deletecert.js
+++ b/security/manager/pki/resources/content/deletecert.js
@@ -1,21 +1,34 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 /* import-globals-from pippki.js */
 "use strict";
 
-const { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
+/**
+ * @file Implements the functionality of deletecert.xul: a dialog that allows a
+ *       user to confirm whether to delete certain certificates.
+ * @argument {String} window.arguments[0]
+ *           One of the tab IDs listed in certManager.xul.
+ * @argument {nsICertTreeItem[]} window.arguments[1]
+ *           An array of cert tree items representing the certs to delete.
+ * @argument {DeleteCertReturnValues} window.arguments[2]
+ *           Object holding the return values of calling the dialog.
+ */
 
 /**
- * Param block to get passed in args and to set return values to.
- * @type nsIDialogParamBlock
+ * @typedef DeleteCertReturnValues
+ * @type Object
+ * @property {Boolean} deleteConfirmed
+ *           Set to true if the user confirmed deletion of the given certs,
+ *           false otherwise.
  */
-var gParams;
+
+const { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
 
 /**
  * Returns the most appropriate string to represent the given nsICertTreeItem.
  * @param {nsICertTreeItem} certTreeItem
  *        The item to represent.
  * @returns {String}
  *          A representative string.
  */
@@ -36,21 +49,21 @@ function certTreeItemToString(certTreeIt
       return attribute;
     }
   }
 
   let bundle = document.getElementById("pippki_bundle");
   return bundle.getFormattedString("certWithSerial", [cert.serialNumber]);
 }
 
-function setWindowName()
-{
-  gParams = window.arguments[0].QueryInterface(Ci.nsIDialogParamBlock);
-
-  let typeFlag = gParams.GetString(0);
+/**
+ * onload() handler.
+ */
+function onLoad() {
+  let typeFlag = window.arguments[0];
   let bundle = document.getElementById("pippki_bundle");
   let title;
   let confirm;
   let impact;
 
   switch (typeFlag) {
     case "mine_tab":
       title = bundle.getString("deleteUserCertTitle");
@@ -81,31 +94,41 @@ function setWindowName()
       return;
   }
 
   document.title = title;
 
   setText("confirm", confirm);
 
   let box = document.getElementById("certlist");
-  for (let x = 0; x < gParams.objects.length; x++) {
+  let certTreeItems = window.arguments[1];
+  for (let certTreeItem of certTreeItems) {
     let listItem = document.createElement("richlistitem");
     let label = document.createElement("label");
-    let certTreeItem = gParams.objects.queryElementAt(x, Ci.nsICertTreeItem);
     label.setAttribute("value", certTreeItemToString(certTreeItem));
     listItem.appendChild(label);
     box.appendChild(listItem);
   }
 
   setText("impact", impact);
 }
 
-function doOK()
-{
-  gParams.SetInt(1, 1); // means OK
+/**
+ * ondialogaccept() handler.
+ *
+ * @returns {Boolean} true to make the dialog close, false otherwise.
+ */
+function onDialogAccept() {
+  let retVals = window.arguments[2];
+  retVals.deleteConfirmed = true;
   return true;
 }
 
-function doCancel()
-{
-  gParams.SetInt(1, 0); // means CANCEL
+/**
+ * ondialogcancel() handler.
+ *
+ * @returns {Boolean} true to make the dialog close, false otherwise.
+ */
+function onDialogCancel() {
+  let retVals = window.arguments[2];
+  retVals.deleteConfirmed = false;
   return true;
 }

--- a/security/manager/pki/resources/content/deletecert.xul
+++ b/security/manager/pki/resources/content/deletecert.xul
@@ -2,23 +2,23 @@
 <!-- This Source Code Form is subject to the terms of the Mozilla Public
    - License, v. 2.0. If a copy of the MPL was not distributed with this
    - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
 
 <?xml-stylesheet href="chrome://global/skin/" type="text/css"?>
 
 <!DOCTYPE dialog SYSTEM "chrome://pippki/locale/certManager.dtd">
 
-<dialog id="deleteCertificate" 
+<dialog id="deleteCertificate"
   title="&certmgr.deletecert.title;"
   xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
-  onload="setWindowName();"
+  onload="onLoad();"
   buttons="accept,cancel"
-  ondialogaccept="return doOK();"
-  ondialogcancel="return doCancel();">
+  ondialogaccept="return onDialogAccept();"
+  ondialogcancel="return onDialogCancel();">
 
   <stringbundle id="pippki_bundle" src="chrome://pippki/locale/pippki.properties"/>
 
   <script type="application/javascript" src="chrome://pippki/content/deletecert.js"/>
   <script type="application/javascript" src="pippki.js" />
 
   <description id="confirm" style="width: 400px;"/>
   <richlistbox id="certlist" class="box-padded" flex="1"

--- a/security/manager/ssl/tests/mochitest/browser/browser_deleteCert_ui.js
+++ b/security/manager/ssl/tests/mochitest/browser/browser_deleteCert_ui.js
@@ -6,19 +6,19 @@
 // Tests various aspects of the cert delete confirmation dialog.
 // Among other things, tests that for each type of cert that can be deleted:
 // 1. The various lines of explanation text are correctly set.
 // 2. The implementation correctly falls back through multiple cert attributes
 //    to determine what to display to represent a cert.
 
 /**
  * An array of tree items corresponding to TEST_CASES.
- * @type nsIMutableArray<nsICertTreeItem>
+ * @type nsICertTreeItem[]
  */
-var gCertArray = Cc["@mozilla.org/array;1"].createInstance(Ci.nsIMutableArray);
+var gCertArray = [];
 
 const FAKE_HOST_PORT = "Fake host and port";
 
 /**
  * @typedef {TestCase}
  * @type Object
  * @property {String} certFilename
  *           Filename of the cert, or null if we don't want to import a cert for
@@ -51,30 +51,28 @@ const TEST_CASES = [
  * Opens the cert delete confirmation dialog.
  *
  * @param {String} tabID
  *        The ID of the cert category tab the certs to delete belong to.
  * @returns {Promise}
  *          A promise that resolves when the dialog has finished loading, with
  *          an array consisting of:
  *            1. The window of the opened dialog.
- *            2. The nsIDialogParamBlock passed to the dialog.
+ *            2. The return value object passed to the dialog.
  */
 function openDeleteCertConfirmDialog(tabID) {
-  let params = Cc["@mozilla.org/embedcomp/dialogparam;1"]
-                 .createInstance(Ci.nsIDialogParamBlock);
-  params.SetString(0, tabID);
-  params.objects = gCertArray;
-
+  let retVals = {
+    deleteConfirmed: false,
+  };
   let win = window.openDialog("chrome://pippki/content/deletecert.xul", "", "",
-                              params);
+                              tabID, gCertArray, retVals);
   return new Promise((resolve, reject) => {
     win.addEventListener("load", function onLoad() {
       win.removeEventListener("load", onLoad);
-      resolve([win, params]);
+      resolve([win, retVals]);
     });
   });
 }
 
 add_task(function* setup() {
   for (let testCase of TEST_CASES) {
     let cert = null;
     if (testCase.certFilename) {
@@ -86,34 +84,34 @@ add_task(function* setup() {
       QueryInterface(iid) {
         if (iid.equals(Ci.nsICertTreeItem)) {
           return this;
         }
 
         throw new Error(Cr.NS_ERROR_NO_INTERFACE);
       }
     };
-    gCertArray.appendElement(certTreeItem, false);
+    gCertArray.push(certTreeItem);
   }
 });
 
 /**
  * Test helper for the below test cases.
  *
  * @param {String} tabID
  *        ID of the cert category tab the certs to delete belong to.
  * @param {String} expectedTitle
  *        Title the dialog is expected to have.
  * @param {String} expectedConfirmMsg
  *        Confirmation message the dialog is expected to show.
  * @param {String} expectedImpact
  *        Impact the dialog is expected to show.
  */
 function* testHelper(tabID, expectedTitle, expectedConfirmMsg, expectedImpact) {
-  let [win, params] = yield openDeleteCertConfirmDialog(tabID);
+  let [win, retVals] = yield openDeleteCertConfirmDialog(tabID);
   let certList = win.document.getElementById("certlist");
 
   Assert.equal(win.document.title, expectedTitle,
                `Actual and expected titles should match for ${tabID}`);
   Assert.equal(win.document.getElementById("confirm").textContent,
                expectedConfirmMsg,
                `Actual and expected confirm message should match for ${tabID}`);
   Assert.equal(win.document.getElementById("impact").textContent,
@@ -191,27 +189,27 @@ add_task(function* testDeleteOtherCerts(
     "Are you sure you want to delete these certificates?";
   const expectedImpact = "";
   yield* testHelper("orphan_tab", expectedTitle, expectedConfirmMsg,
                     expectedImpact);
 });
 
 // Test that the right values are returned when the dialog is accepted.
 add_task(function* testAcceptDialogReturnValues() {
-  let [win, params] = yield openDeleteCertConfirmDialog("ca_tab" /*arbitrary*/);
+  let [win, retVals] = yield openDeleteCertConfirmDialog("ca_tab" /*arbitrary*/);
   info("Accepting dialog");
   win.document.getElementById("deleteCertificate").acceptDialog();
   yield BrowserTestUtils.windowClosed(win);
 
-  Assert.equal(params.GetInt(1), 1,
-               "1 should be returned to signal user accepted");
+  Assert.ok(retVals.deleteConfirmed,
+            "Return value should signal user accepted");
 });
 
 // Test that the right values are returned when the dialog is canceled.
 add_task(function* testCancelDialogReturnValues() {
-  let [win, params] = yield openDeleteCertConfirmDialog("ca_tab" /*arbitrary*/);
+  let [win, retVals] = yield openDeleteCertConfirmDialog("ca_tab" /*arbitrary*/);
   info("Canceling dialog");
   win.document.getElementById("deleteCertificate").cancelDialog();
   yield BrowserTestUtils.windowClosed(win);
 
-  Assert.equal(params.GetInt(1), 0,
-               "0 should be returned to signal user canceled");
+  Assert.ok(!retVals.deleteConfirmed,
+            "Return value should signal user did not accept");
 });