diff --git a/dom/security/test/mixedcontentblocker/mochitest.ini b/dom/security/test/mixedcontentblocker/mochitest.ini
index 0051eb89b949..05a1e0c056b0 100644
--- a/dom/security/test/mixedcontentblocker/mochitest.ini
+++ b/dom/security/test/mixedcontentblocker/mochitest.ini
@@ -14,7 +14,7 @@ support-files =
   file_server.sjs
 
 [test_main.html]
-skip-if = buildapp == 'mulet' || buildapp == 'b2g' || toolkit == 'android' || e10s #TIMED_OUT, SSL_REQUIRED # Bug 1141029 Mulet parity with B2G Desktop for TC
+skip-if = buildapp == 'mulet' || buildapp == 'b2g' || toolkit == 'android' #TIMED_OUT, SSL_REQUIRED # Bug 1141029 Mulet parity with B2G Desktop for TC
 [test_bug803225.html]
 skip-if = buildapp == 'mulet' || buildapp == 'b2g' || toolkit == 'android' || e10s #TIMED_OUT, SSL_REQUIRED # Bug 1141029 Mulet parity with B2G Desktop for TC
 [test_frameNavigation.html]
diff --git a/dom/security/test/mixedcontentblocker/test_main.html b/dom/security/test/mixedcontentblocker/test_main.html
index abaf7f029878..646fe4c60f52 100644
--- a/dom/security/test/mixedcontentblocker/test_main.html
+++ b/dom/security/test/mixedcontentblocker/test_main.html
@@ -13,9 +13,6 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=62178
   <script>
   SpecialPowers.setTestPluginEnabledState(SpecialPowers.Ci.nsIPluginTag.STATE_ENABLED, "Test Plug-in");
 
-  var origBlockDisplay = SpecialPowers.getBoolPref("security.mixed_content.block_display_content");
-  var origBlockActive = SpecialPowers.getBoolPref("security.mixed_content.block_active_content");
-
   var counter = 0;
   var settings = [ [true, true], [true, false], [false, true], [false, false] ];
 
@@ -23,16 +20,18 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=62178
   var blockDisplay;
 
   //Cycle through 4 different preference settings.
-  function changePrefs(x) {
-    SpecialPowers.setBoolPref("security.mixed_content.block_display_content", settings[x][0]);
-    SpecialPowers.setBoolPref("security.mixed_content.block_active_content", settings[x][1]);
-    blockDisplay = SpecialPowers.getBoolPref("security.mixed_content.block_display_content");
-    blockActive = SpecialPowers.getBoolPref("security.mixed_content.block_active_content");
-  }
+  function changePrefs(otherPrefs, callback) {
+    let basePrefs = [["security.mixed_content.block_display_content", settings[counter][0]],
+                     ["security.mixed_content.block_active_content", settings[counter][1]]];
+    let newPrefs = basePrefs.concat(otherPrefs);
 
-  //Set the first set of settings (true, true) and increment the counter.
-  changePrefs(counter);
-  counter++;
+    SpecialPowers.pushPrefEnv({"set": newPrefs}, function () {
+      blockDisplay = SpecialPowers.getBoolPref("security.mixed_content.block_display_content");
+      blockActive = SpecialPowers.getBoolPref("security.mixed_content.block_active_content");
+      counter++;
+      callback();
+    });
+  }
 
   var testsToRun = {
     iframe: false,
@@ -69,23 +68,18 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=62178
          testsToRun[prop] = false;
        }
       //call to change the preferences
-      changePrefs(counter);
-      counter++;
-      log("\nblockDisplay set to "+blockDisplay+", blockActive set to "+blockActive+".");
-      reloadFrame();
+      changePrefs([], function() {
+        log("\nblockDisplay set to "+blockDisplay+", blockActive set to "+blockActive+".");
+        reloadFrame();
+      });
     }
     else {
-      //set the prefs back to what they were set to originally
-      SpecialPowers.setBoolPref("security.mixed_content.block_display_content", origBlockDisplay);
-      SpecialPowers.setBoolPref("security.mixed_content.block_active_content", origBlockActive);
       SimpleTest.finish();
     }
   }
 
   var firstTest = true;
 
-  // listen for a messages from the mixed content test harness
-  window.addEventListener("message", receiveMessage, false);
   function receiveMessage(event) {
     if(firstTest) {
       log("blockActive set to "+blockActive+", blockDisplay set to "+blockDisplay+".");
@@ -167,13 +161,17 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=62178
     checkTestsCompleted();
   }
 
-  // Enable <picture> and <img srcset> for test
-  SpecialPowers.pushPrefEnv({'set': [[ "dom.image.srcset.enabled", true ],
-                                     [ "dom.image.picture.enabled", true ]] },
-                            function() {
-    // Kick off test
-    reloadFrame();
-  });
+  //Set the first set of mixed content settings and increment the counter.
+  //Enable <picture> and <img srcset> for the test.
+  changePrefs([[ "dom.image.srcset.enabled", true ], [ "dom.image.picture.enabled", true ]],
+    function() {
+      //listen for a messages from the mixed content test harness
+      window.addEventListener("message", receiveMessage, false);
+
+      //Kick off test
+      reloadFrame();
+    }
+  );
 
   SimpleTest.waitForExplicitFinish();