diff --git a/dom/html/test/mochitest.ini b/dom/html/test/mochitest.ini
index 70bd4c62ffc8d..45982ec4781e6 100644
--- a/dom/html/test/mochitest.ini
+++ b/dom/html/test/mochitest.ini
@@ -582,7 +582,8 @@ skip-if = toolkit == 'android'
 [test_bug741266.html]
 skip-if = buildapp == "mulet" || buildapp == "b2g" || toolkit == "android" || toolkit == "windows" || e10s # b2g(needs control of popup window size) b2g-debug(needs control of popup window size) b2g-desktop(needs control of popup window size) windows(bug 1234520)
 [test_non-ascii-cookie.html]
-skip-if = buildapp == 'b2g' || e10s
+skip-if = buildapp == 'b2g'
+support-files = file_cookiemanager.js
 [test_bug765780.html]
 [test_bug871161.html]
 skip-if = (buildapp == 'b2g' && toolkit != 'gonk') #Bug 931116, b2g desktop specific, initial triage
diff --git a/dom/html/test/test_non-ascii-cookie.html b/dom/html/test/test_non-ascii-cookie.html
index fc307265a659e..ab96ac07c2dc4 100644
--- a/dom/html/test/test_non-ascii-cookie.html
+++ b/dom/html/test/test_non-ascii-cookie.html
@@ -20,38 +20,40 @@
 
 /** Test for non-ASCII cookie values **/
 
-var [Cc, Ci] = [SpecialPowers.Cc, SpecialPowers.Ci];
+SimpleTest.waitForExplicitFinish();
+
+var gScript = SpecialPowers.loadChromeScript(SimpleTest.getTestFileURL("file_cookiemanager.js"));
 
-var cm = Cc["@mozilla.org/cookiemanager;1"].getService(Ci.nsICookieManager);
 function getCookieFromManager() {
-  var values = [];
-  var host = location.hostname;
-  var path = location.pathname;
-  path = path.substring(0, path.lastIndexOf("/") + 1);
-  var e = cm.enumerator;
-  while (e.hasMoreElements()) {
-    var cookie = e.getNext().QueryInterface(Ci.nsICookie);
-    if (!cookie) {
-      break;
-    }
-    if (host != cookie.host || path != cookie.path) {
-      continue;
-    }
-    values.push(cookie.name + "=" + cookie.value);
-  }
-  return values.join("; ");
+  return new Promise(resolve => {
+    gScript.addMessageListener("getCookieFromManager:return", function gcfm({ cookie }) {
+      gScript.removeMessageListener("getCookieFromManager:return", gcfm);
+      resolve(cookie);
+    });
+    gScript.sendAsyncMessage("getCookieFromManager", { host: location.hostname, path: location.pathname });
+  });
 }
 
 var c = document.cookie;
 is(document.cookie, 'abc=012©ABC\ufffdDEF', "document.cookie should be decoded as UTF-8");
-is(getCookieFromManager(), document.cookie, "nsICookieManager should be consistent with document.cookie");
-var newCookie = 'def=∼≩≭≧∯≳≲≣∽≸≸∺≸∠≯≮≥≲≲≯≲∽≡≬≥≲≴∨∱∩∾';
-document.cookie = newCookie;
-is(document.cookie, c + '; ' + newCookie, "document.cookie should be encoded as UTF-8");
-is(getCookieFromManager(), document.cookie, "nsICookieManager should be consistent with document.cookie");
-var date1 = new Date();
-date1.setTime(0);
-document.cookie = newCookie + 'def=;expires=' + date1.toGMTString();
+
+var newCookie;
+
+getCookieFromManager().then((cookie) => {
+  is(cookie, document.cookie, "nsICookieManager should be consistent with document.cookie");
+  newCookie = 'def=∼≩≭≧∯≳≲≣∽≸≸∺≸∠≯≮≥≲≲≯≲∽≡≬≥≲≴∨∱∩∾';
+  document.cookie = newCookie;
+  is(document.cookie, c + '; ' + newCookie, "document.cookie should be encoded as UTF-8");
+
+  return getCookieFromManager();
+}).then((cookie) => {
+  is(cookie, document.cookie, "nsICookieManager should be consistent with document.cookie");
+  var date1 = new Date();
+  date1.setTime(0);
+  document.cookie = newCookie + 'def=;expires=' + date1.toGMTString();
+  gScript.destroy();
+  SimpleTest.finish();
+});
 </script>
 </pre>
 </body>
diff --git a/extensions/cookie/test/file_chromecommon.js b/extensions/cookie/test/file_chromecommon.js
new file mode 100644
index 0000000000000..4383876b25b5e
--- /dev/null
+++ b/extensions/cookie/test/file_chromecommon.js
@@ -0,0 +1,15 @@
+let { classes: Cc, utils: Cu, interfaces: Ci } = Components;
+
+let cs = Cc["@mozilla.org/cookiemanager;1"]
+           .getService(Ci.nsICookieManager2);
+
+addMessageListener("getCookieCountAndClear", () => {
+  let count = 0;
+  for (let list = cs.enumerator; list.hasMoreElements(); list.getNext())
+    ++count;
+  cs.removeAll();
+
+  sendAsyncMessage("getCookieCountAndClear:return", { count });
+});
+
+cs.removeAll();
diff --git a/extensions/cookie/test/file_testcommon.js b/extensions/cookie/test/file_testcommon.js
index 0058f308ea439..3ee53c52cb56b 100644
--- a/extensions/cookie/test/file_testcommon.js
+++ b/extensions/cookie/test/file_testcommon.js
@@ -1,45 +1,43 @@
+const SCRIPT_URL = SimpleTest.getTestFileURL("file_chromecommon.js");
+
 var gExpectedCookies;
 var gExpectedLoads;
 
 var gPopup;
 
+var gScript;
+
 var gLoads = 0;
 
 function setupTest(uri, cookies, loads) {
   SimpleTest.waitForExplicitFinish();
 
-  SpecialPowers.Cc["@mozilla.org/preferences-service;1"]
-               .getService(SpecialPowers.Ci.nsIPrefBranch)
-               .setIntPref("network.cookie.cookieBehavior", 1);
-
-  var cs = SpecialPowers.Cc["@mozilla.org/cookiemanager;1"]
-                        .getService(SpecialPowers.Ci.nsICookieManager2);
-  cs.removeAll();
+  var prefSet = new Promise(resolve => {
+    SpecialPowers.pushPrefEnv({ set: [["network.cookie.cookieBehavior", 1]] }, resolve);
+  });
 
+  gScript = SpecialPowers.loadChromeScript(SCRIPT_URL);
   gExpectedCookies = cookies;
   gExpectedLoads = loads;
 
   // Listen for MessageEvents.
   window.addEventListener("message", messageReceiver, false);
 
-  // load a window which contains an iframe; each will attempt to set
-  // cookies from their respective domains.
-  gPopup = window.open(uri, 'hai', 'width=100,height=100');
+  prefSet.then(() => {
+    // load a window which contains an iframe; each will attempt to set
+    // cookies from their respective domains.
+    gPopup = window.open(uri, 'hai', 'width=100,height=100');
+  });
 }
 
-function finishTest()
-{
-  SpecialPowers.Cc["@mozilla.org/preferences-service;1"]
-               .getService(SpecialPowers.Ci.nsIPrefBranch)
-               .clearUserPref("network.cookie.cookieBehavior");
-
+function finishTest() {
+  gScript.destroy();
   SimpleTest.finish();
 }
 
 /** Receives MessageEvents to this window. */
 // Count and check loads.
-function messageReceiver(evt)
-{
+function messageReceiver(evt) {
   is(evt.data, "message", "message data received from popup");
   if (evt.data != "message") {
     gPopup.close();
@@ -64,13 +62,9 @@ function runTest() {
   // set a cookie from a domain of "localhost"
   document.cookie = "oh=hai";
 
-  var cs = SpecialPowers.Cc["@mozilla.org/cookiemanager;1"]
-                        .getService(SpecialPowers.Ci.nsICookieManager);
-  var count = 0;
-  for(var list = cs.enumerator; list.hasMoreElements(); list.getNext())
-    ++count;
-  is(count, gExpectedCookies, "total number of cookies");
-  cs.removeAll();
-
-  finishTest();
+  gScript.addMessageListener("getCookieCountAndClear:return", ({ count }) => {
+    is(count, gExpectedCookies, "total number of cookies");
+    finishTest();
+  });
+  gScript.sendAsyncMessage("getCookieCountAndClear");
 }
diff --git a/extensions/cookie/test/file_testloadflags.js b/extensions/cookie/test/file_testloadflags.js
index 1d21b50e17413..9cf4a15a6bded 100644
--- a/extensions/cookie/test/file_testloadflags.js
+++ b/extensions/cookie/test/file_testloadflags.js
@@ -1,3 +1,5 @@
+const SCRIPT_URL = SimpleTest.getTestFileURL('file_testloadflags_chromescript.js');
+
 var gExpectedCookies;
 var gExpectedHeaders;
 var gExpectedLoads;
@@ -10,113 +12,50 @@ var gLoads = 0;
 
 // setupTest() is run from 'onload='.
 function setupTest(uri, domain, cookies, loads, headers) {
-  ok(true, "setupTest uri: " + uri + " domain: " + domain + " cookies: " + cookies +
-           " loads: " + loads + " headers: " + headers);
+  info("setupTest uri: " + uri + " domain: " + domain + " cookies: " + cookies +
+       " loads: " + loads + " headers: " + headers);
 
   SimpleTest.waitForExplicitFinish();
 
-  SpecialPowers.Cc["@mozilla.org/preferences-service;1"]
-               .getService(SpecialPowers.Ci.nsIPrefBranch)
-               .setIntPref("network.cookie.cookieBehavior", 1);
-
-  var cs = SpecialPowers.Cc["@mozilla.org/cookiemanager;1"]
-                        .getService(SpecialPowers.Ci.nsICookieManager2);
-
-  ok(true, "we are going to remove these cookies");
-  var count = 0;
-  var list = cs.enumerator;
-  while (list.hasMoreElements()) {
-    var cookie = list.getNext().QueryInterface(SpecialPowers.Ci.nsICookie);
-    ok(true, "cookie: " + cookie);
-    ok(true, "cookie host " + cookie.host + " path " + cookie.path + " name " + cookie.name +
-       " value " + cookie.value + " isSecure " + cookie.isSecure + " expires " + cookie.expires);
-    ++count;
-  }
-  ok(true, count + " cookies");
-
-  cs.removeAll();
-  cs.add(domain, "", "oh", "hai", false, false, true, Math.pow(2, 62));
-  is(cs.countCookiesFromHost(domain), 1, "number of cookies for domain " + domain);
+  var prefSet = new Promise(resolve => {
+    SpecialPowers.pushPrefEnv({ set: [["network.cookie.cookieBehavior", 1]] }, resolve);
+  });
 
   gExpectedCookies = cookies;
   gExpectedLoads = loads;
   gExpectedHeaders = headers;
 
-  gObs = new obs();
+  gScript = SpecialPowers.loadChromeScript(SCRIPT_URL);
+  gScript.addMessageListener("info", ({ str }) => info(str));
+  gScript.addMessageListener("ok", ({ c, m }) => ok(c, m));
+  gScript.addMessageListener("observer:gotCookie", ({ cookie, uri }) => {
+    isnot(cookie.indexOf("oh=hai"), -1,
+          "cookie 'oh=hai' is in header for " + uri);
+    ++gHeaders;
+  });
+
+  var scriptReady = new Promise(resolve => {
+    gScript.addMessageListener("init:return", resolve);
+    gScript.sendAsyncMessage("init", { domain });
+  });
+
   // Listen for MessageEvents.
   window.addEventListener("message", messageReceiver, false);
 
-  // load a window which contains an iframe; each will attempt to set
-  // cookies from their respective domains.
-  gPopup = window.open(uri, 'hai', 'width=100,height=100');
+  Promise.all([ prefSet, scriptReady ]).then(() => {
+    // load a window which contains an iframe; each will attempt to set
+    // cookies from their respective domains.
+    gPopup = window.open(uri, 'hai', 'width=100,height=100');
+  });
 }
 
 function finishTest()
 {
-  gObs.remove();
-
-  SpecialPowers.Cc["@mozilla.org/preferences-service;1"]
-               .getService(SpecialPowers.Ci.nsIPrefBranch)
-               .clearUserPref("network.cookie.cookieBehavior");
-
-  SimpleTest.finish();
-}
-
-// Count headers.
-function obs () {
-  netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
-
-  ok(true, "adding observer");
-
-  this.window = window;
-  this.os = SpecialPowers.Cc["@mozilla.org/observer-service;1"]
-                         .getService(SpecialPowers.Ci.nsIObserverService);
-  this.os.addObserver(this, "http-on-modify-request", false);
-}
-
-obs.prototype = {
-  observe: function obs_observe (theSubject, theTopic, theData)
-  {
-    ok(true, "theSubject " + theSubject);
-    ok(true, "theTopic " + theTopic);
-    ok(true, "theData " + theData);
-
-    var channel = theSubject.QueryInterface(
-                    this.window.SpecialPowers.Ci.nsIHttpChannel);
-    ok(true, "channel " + channel);
-    try {
-      ok(true, "channel.URI " + channel.URI);
-      ok(true, "channel.URI.spec " + channel.URI.spec);
-      channel.visitRequestHeaders({
-        visitHeader: function(aHeader, aValue) {
-          ok(true, aHeader + ": " + aValue);
-        }});
-    } catch (err) {
-      ok(false, "catch error " + err);
-    }
-
-    // Ignore notifications we don't care about (like favicons)
-    if (channel.URI.spec.indexOf(
-          "http://example.org/tests/extensions/cookie/test/") == -1) {
-      ok(true, "ignoring this one");
-      return;
-    }
-
-    this.window.isnot(channel.getRequestHeader("Cookie").indexOf("oh=hai"), -1,
-                      "cookie 'oh=hai' is in header for " + channel.URI.spec);
-    ++gHeaders;
-  },
-
-  remove: function obs_remove()
-  {
-    netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
-
-    ok(true, "removing observer");
-
-    this.os.removeObserver(this, "http-on-modify-request");
-    this.os = null;
-    this.window = null;
-  }
+  gScript.addMessageListener("shutdown:return", () => {
+    gScript.destroy();
+    SimpleTest.finish();
+  });
+  gScript.sendAsyncMessage("shutdown");
 }
 
 /** Receives MessageEvents to this window. */
@@ -126,13 +65,13 @@ function messageReceiver(evt)
   ok(evt.data == "f_lf_i msg data img" || evt.data == "f_lf_i msg data page",
      "message data received from popup");
   if (evt.data == "f_lf_i msg data img") {
-    ok(true, "message data received from popup for image");
+    info("message data received from popup for image");
   }
   if (evt.data == "f_lf_i msg data page") {
-    ok(true, "message data received from popup for page");
+    info("message data received from popup for page");
   }
   if (evt.data != "f_lf_i msg data img" && evt.data != "f_lf_i msg data page") {
-    ok(true, "got this message but don't know what it is " + evt.data);
+    info("got this message but don't know what it is " + evt.data);
     gPopup.close();
     window.removeEventListener("message", messageReceiver, false);
 
@@ -156,20 +95,10 @@ function runTest() {
   document.cookie = "o=noes";
 
   is(gHeaders, gExpectedHeaders, "number of observed request headers");
+  gScript.addMessageListener("getCookieCount:return", ({ count }) => {
+    is(count, gExpectedCookies, "total number of cookies");
+    finishTest();
+  });
 
-  var cs = SpecialPowers.Cc["@mozilla.org/cookiemanager;1"]
-                        .getService(SpecialPowers.Ci.nsICookieManager);
-  var count = 0;
-  var list = cs.enumerator;
-  while (list.hasMoreElements()) {
-    var cookie = list.getNext().QueryInterface(SpecialPowers.Ci.nsICookie);
-    ok(true, "cookie: " + cookie);
-    ok(true, "cookie host " + cookie.host + " path " + cookie.path + " name " + cookie.name +
-       " value " + cookie.value + " isSecure " + cookie.isSecure + " expires " + cookie.expires);
-    ++count;
-  }
-  is(count, gExpectedCookies, "total number of cookies");
-  cs.removeAll();
-
-  finishTest();
+  gScript.sendAsyncMessage("getCookieCount");
 }
diff --git a/extensions/cookie/test/file_testloadflags_chromescript.js b/extensions/cookie/test/file_testloadflags_chromescript.js
new file mode 100644
index 0000000000000..ad9b0fe53e230
--- /dev/null
+++ b/extensions/cookie/test/file_testloadflags_chromescript.js
@@ -0,0 +1,112 @@
+let { classes: Cc, interfaces: Ci } = Components;
+
+var gObs;
+
+function info(s) {
+  sendAsyncMessage("info", { str: String(s) });
+}
+
+function ok(c, m) {
+  sendAsyncMessage("ok", { c, m });
+}
+
+function is(a, b, m) {
+  ok(Object.is(a, b), m + " (" + a + " === " + b + ")");
+}
+
+// Count headers.
+function obs() {
+  info("adding observer");
+
+  this.os = Cc["@mozilla.org/observer-service;1"]
+              .getService(Ci.nsIObserverService);
+  this.os.addObserver(this, "http-on-modify-request", false);
+}
+
+obs.prototype = {
+  observe(theSubject, theTopic, theData) {
+    info("theSubject " + theSubject);
+    info("theTopic " + theTopic);
+    info("theData " + theData);
+
+    var channel = theSubject.QueryInterface(Ci.nsIHttpChannel);
+    info("channel " + channel);
+    try {
+      info("channel.URI " + channel.URI);
+      info("channel.URI.spec " + channel.URI.spec);
+      channel.visitRequestHeaders({
+        visitHeader: function(aHeader, aValue) {
+          info(aHeader + ": " + aValue);
+        }});
+    } catch (err) {
+      ok(false, "catch error " + err);
+    }
+
+    // Ignore notifications we don't care about (like favicons)
+    if (channel.URI.spec.indexOf(
+          "http://example.org/tests/extensions/cookie/test/") == -1) {
+      info("ignoring this one");
+      return;
+    }
+
+    sendAsyncMessage("observer:gotCookie",
+                     { cookie: channel.getRequestHeader("Cookie"),
+                       uri: channel.URI.spec });
+  },
+
+  remove() {
+    info("removing observer");
+
+    this.os.removeObserver(this, "http-on-modify-request");
+    this.os = null;
+  }
+}
+
+function getCookieCount(cs) {
+  let count = 0;
+  let list = cs.enumerator;
+  while (list.hasMoreElements()) {
+    let cookie = list.getNext().QueryInterface(Ci.nsICookie);
+    info("cookie: " + cookie);
+    info("cookie host " + cookie.host + " path " + cookie.path + " name " + cookie.name +
+         " value " + cookie.value + " isSecure " + cookie.isSecure + " expires " + cookie.expires);
+    ++count;
+  }
+
+  return count;
+}
+
+addMessageListener("init", ({ domain }) => {
+  let cs = Cc["@mozilla.org/cookiemanager;1"]
+             .getService(Ci.nsICookieManager2);
+
+  info("we are going to remove these cookies");
+
+  let count = getCookieCount(cs);
+  info(count + " cookies");
+
+  cs.removeAll();
+  cs.add(domain, "", "oh", "hai", false, false, true, Math.pow(2, 62));
+  is(cs.countCookiesFromHost(domain), 1, "number of cookies for domain " + domain);
+
+  gObs = new obs();
+  sendAsyncMessage("init:return");
+});
+
+addMessageListener("getCookieCount", () => {
+  let cs = Cc["@mozilla.org/cookiemanager;1"]
+             .getService(Ci.nsICookieManager);
+  let count = getCookieCount(cs);
+
+  cs.removeAll();
+  sendAsyncMessage("getCookieCount:return", { count });
+});
+
+addMessageListener("shutdown", () => {
+  gObs.remove();
+
+  let cs = Cc["@mozilla.org/cookiemanager;1"]
+             .getService(Ci.nsICookieManager2);
+  cs.removeAll();
+  sendAsyncMessage("shutdown:return");
+});
diff --git a/extensions/cookie/test/mochitest.ini b/extensions/cookie/test/mochitest.ini
index 794dce7d52e09..5253274f188cb 100644
--- a/extensions/cookie/test/mochitest.ini
+++ b/extensions/cookie/test/mochitest.ini
@@ -1,10 +1,11 @@
 [DEFAULT]
-skip-if = buildapp == 'b2g' || e10s
+skip-if = buildapp == 'b2g'
 support-files =
   beltzner.jpg
   beltzner.jpg^headers^
   damonbowling.jpg
   damonbowling.jpg^headers^
+  file_chromecommon.js
   file_domain_hierarchy_inner.html
   file_domain_hierarchy_inner_inner.html
   file_domain_hierarchy_inner_inner_inner.html
@@ -18,6 +19,7 @@ support-files =
   file_subdomain_inner.html
   file_testcommon.js
   file_testloadflags.js
+  file_testloadflags_chromescript.js
   image1.png
   image1.png^headers^
   image2.png