--- a/browser/base/content/test/general/browser.ini
+++ b/browser/base/content/test/general/browser.ini
@@ -514,17 +514,16 @@ skip-if = e10s # Bug 1094240 - has findb
 [browser_registerProtocolHandler_notification.js]
 [browser_no_mcb_on_http_site.js]
 tags = mcb
 [browser_bug1104165-switchtab-decodeuri.js]
 [browser_bug1003461-switchtab-override.js]
 [browser_bug1024133-switchtab-override-keynav.js]
 [browser_bug1025195_switchToTabHavingURI_aOpenParams.js]
 [browser_addCertException.js]
-skip-if = e10s # Bug 1100687 - test directly manipulates content (content.document.getElementById)
 [browser_bug1045809.js]
 tags = mcb
 [browser_bug1225194-remotetab.js]
 [browser_e10s_switchbrowser.js]
 [browser_e10s_about_process.js]
 [browser_e10s_chrome_process.js]
 [browser_e10s_javascript.js]
 [browser_blockHPKP.js]

--- a/browser/base/content/test/general/browser_addCertException.js
+++ b/browser/base/content/test/general/browser_addCertException.js
@@ -11,83 +11,60 @@
 // the site, including showing the right identity box and control center icons.
 function test() {
   waitForExplicitFinish();
   whenNewTabLoaded(window, loadBadCertPage);
 }
 
 // Attempt to load https://expired.example.com (which has an expired cert).
 function loadBadCertPage() {
-  gBrowser.addProgressListener(certErrorProgressListener);
+  let pageLoaded = promiseErrorPageLoaded(gBrowser.selectedBrowser);
   gBrowser.selectedBrowser.loadURI("https://expired.example.com");
+  Services.obs.addObserver(certExceptionDialogObserver,
+                           "cert-exception-ui-ready", false);
+  pageLoaded.then(function() {
+    ContentTask.spawn(gBrowser.selectedBrowser, null, function*() {
+      content.document.getElementById("exceptionDialogButton").click();
+    });
+  });
 }
 
-// The browser should load about:certerror. When This happens, click the
-// button to open the certificate exception dialog.
-var certErrorProgressListener = {
-  buttonClicked: false,
-
-  onStateChange: function(aWebProgress, aRequest, aStateFlags, aStatus) {
-    if (aStateFlags & Ci.nsIWebProgressListener.STATE_STOP) {
-      let self = this;
-      // Can't directly call button.click() in onStateChange
-      executeSoon(function() {
-        let button = content.document.getElementById("exceptionDialogButton");
-        // If about:certerror hasn't fully loaded, the button won't be present.
-        // It will eventually be there, however.
-        if (button && !self.buttonClicked) {
-          gBrowser.removeProgressListener(self);
-          Services.obs.addObserver(certExceptionDialogObserver,
-                                   "cert-exception-ui-ready", false);
-          button.click();
-        }
-      });
-    }
-  }
-};
-
 // When the certificate exception dialog has opened, click the button to add
 // an exception.
 const EXCEPTION_DIALOG_URI = "chrome://pippki/content/exceptionDialog.xul";
 var certExceptionDialogObserver = {
   observe: function(aSubject, aTopic, aData) {
     if (aTopic == "cert-exception-ui-ready") {
       Services.obs.removeObserver(this, "cert-exception-ui-ready");
       let certExceptionDialog = getDialog(EXCEPTION_DIALOG_URI);
       ok(certExceptionDialog, "found exception dialog");
       executeSoon(function() {
-        gBrowser.selectedBrowser.addEventListener("load",
-                                                  successfulLoadListener,
-                                                  true);
+        BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser).then(realPageLoaded);
         certExceptionDialog.documentElement.getButton("extra1").click();
       });
     }
   }
 };
 
 // Finally, we should successfully load https://expired.example.com.
-var successfulLoadListener = {
-  handleEvent: function() {
-    gBrowser.selectedBrowser.removeEventListener("load", this, true);
-    checkControlPanelIcons();
-    let certOverrideService = Cc["@mozilla.org/security/certoverride;1"]
-                                .getService(Ci.nsICertOverrideService);
-    certOverrideService.clearValidityOverride("expired.example.com", -1);
-    gBrowser.removeTab(gBrowser.selectedTab);
-    finish();
-  }
+function realPageLoaded() {
+  checkControlPanelIcons();
+  let certOverrideService = Cc["@mozilla.org/security/certoverride;1"]
+                              .getService(Ci.nsICertOverrideService);
+  certOverrideService.clearValidityOverride("expired.example.com", -1);
+  BrowserTestUtils.removeTab(gBrowser.selectedTab).then(finish);
 };
 
 // Check for the correct icons in the identity box and control center.
 function checkControlPanelIcons() {
   let { gIdentityHandler } = gBrowser.ownerGlobal;
   gIdentityHandler._identityBox.click();
   document.getElementById("identity-popup-security-expander").click();
 
-  is_element_visible(document.getElementById("connection-icon"));
+  is_element_visible(document.getElementById("connection-icon"), "Should see connection icon");
   let connectionIconImage = gBrowser.ownerGlobal
         .getComputedStyle(document.getElementById("connection-icon"), "")
         .getPropertyValue("list-style-image");
   let securityViewBG = gBrowser.ownerGlobal
         .getComputedStyle(document.getElementById("identity-popup-securityView"), "")
         .getPropertyValue("background-image");
   let securityContentBG = gBrowser.ownerGlobal
         .getComputedStyle(document.getElementById("identity-popup-security-content"), "")
@@ -127,8 +104,17 @@ function getDialog(aLocation) {
                                   .DOMDocument;
 
       if (childDoc.location.href == aLocation) {
         return childDoc;
       }
     }
   }
 }
+
+function promiseErrorPageLoaded(browser) {
+  return new Promise(resolve => {
+    browser.addEventListener("DOMContentLoaded", function onLoad() {
+      browser.removeEventListener("DOMContentLoaded", onLoad, false, true);
+      resolve();
+    }, false, true);
+  });
+}

--- a/browser/base/content/test/general/head.js
+++ b/browser/base/content/test/general/head.js
@@ -953,22 +953,22 @@ function is_visible(element) {
   if (element.parentNode != element.ownerDocument)
     return is_visible(element.parentNode);
 
   return true;
 }
 
 function is_element_visible(element, msg) {
   isnot(element, null, "Element should not be null, when checking visibility");
-  ok(is_visible(element), msg);
+  ok(is_visible(element), msg || "Element should be visible");
 }
 
 function is_element_hidden(element, msg) {
   isnot(element, null, "Element should not be null, when checking visibility");
-  ok(is_hidden(element), msg);
+  ok(is_hidden(element), msg || "Element should be hidden");
 }
 
 function promisePopupEvent(popup, eventSuffix) {
   let endState = {shown: "open", hidden: "closed"}[eventSuffix];
 
   if (popup.state == endState)
     return Promise.resolve();