--- a/toolkit/components/url-classifier/tests/mochitest/classifierCommon.js
+++ b/toolkit/components/url-classifier/tests/mochitest/classifierCommon.js
@@ -11,17 +11,17 @@ function doUpdate(update) {
           iid.equals(Ci.nsIUrlClassifierUpdateObserver))
         return this;
 
       throw Cr.NS_ERROR_NO_INTERFACE;
     },
     updateUrlRequested: function(url) { },
     streamFinished: function(status) { },
     updateError: function(errorCode) {
-      sendAsyncMessage("updateError", { errorCode });
+      sendAsyncMessage("updateError", errorCode);
     },
     updateSuccess: function(requestedTimeout) {
       sendAsyncMessage("updateSuccess");
     }
   };
 
   let dbService = Cc["@mozilla.org/url-classifier/dbservice;1"]
                   .getService(Ci.nsIUrlClassifierDBService);

--- a/toolkit/components/url-classifier/tests/mochitest/classifierHelper.js
+++ b/toolkit/components/url-classifier/tests/mochitest/classifierHelper.js
@@ -1,115 +1,137 @@
 if (typeof(classifierHelper) == "undefined") {
   var classifierHelper = {};
 }
 
 const CLASSIFIER_COMMON_URL = SimpleTest.getTestFileURL("classifierCommon.js");
-var classifierCommonScript = SpecialPowers.loadChromeScript(CLASSIFIER_COMMON_URL);
+var gScript = SpecialPowers.loadChromeScript(CLASSIFIER_COMMON_URL);
 
 const ADD_CHUNKNUM = 524;
 const SUB_CHUNKNUM = 523;
 const HASHLEN = 32;
 
 // addUrlToDB & removeUrlFromDB are asynchronous, queue the task to ensure
 // the callback follow correct order.
 classifierHelper._updates = [];
 
 // Keep urls added to database, those urls should be automatically
 // removed after test complete.
 classifierHelper._updatesToCleanup = [];
 
 // Pass { url: ..., db: ... } to add url to database,
 // onsuccess/onerror will be called when update complete.
-classifierHelper.addUrlToDB = function(updateData, onsuccess, onerror) {
-  var testUpdate = "";
-  for (var update of updateData) {
-    var LISTNAME = update.db;
-    var CHUNKDATA = update.url;
-    var CHUNKLEN = CHUNKDATA.length;
+classifierHelper.addUrlToDB = function(updateData) {
+  return new Promise(function(resolve, reject) {
+    var testUpdate = "";
+    for (var update of updateData) {
+      var LISTNAME = update.db;
+      var CHUNKDATA = update.url;
+      var CHUNKLEN = CHUNKDATA.length;
 
-    classifierHelper._updatesToCleanup.push(update);
-    testUpdate +=
-      "n:1000\n" +
-      "i:" + LISTNAME + "\n" +
-      "ad:1\n" +
-      "a:" + ADD_CHUNKNUM + ":" + HASHLEN + ":" + CHUNKLEN + "\n" +
-      CHUNKDATA;
-  }
+      classifierHelper._updatesToCleanup.push(update);
+      testUpdate +=
+        "n:1000\n" +
+        "i:" + LISTNAME + "\n" +
+        "ad:1\n" +
+        "a:" + ADD_CHUNKNUM + ":" + HASHLEN + ":" + CHUNKLEN + "\n" +
+        CHUNKDATA;
+    }
 
-  classifierHelper._update(testUpdate, onsuccess, onerror);
+    classifierHelper._update(testUpdate, resolve, reject);
+  });
 }
 
 // Pass { url: ..., db: ... } to remove url from database,
 // onsuccess/onerror will be called when update complete.
-classifierHelper.removeUrlFromDB = function(updateData, onsuccess, onerror) {
-  var testUpdate = "";
-  for (var update of updateData) {
-    var LISTNAME = update.db;
-    var CHUNKDATA = ADD_CHUNKNUM + ":" + update.url;
-    var CHUNKLEN = CHUNKDATA.length;
+classifierHelper.removeUrlFromDB = function(updateData) {
+  return new Promise(function(resolve, reject) {
+    var testUpdate = "";
+    for (var update of updateData) {
+      var LISTNAME = update.db;
+      var CHUNKDATA = ADD_CHUNKNUM + ":" + update.url;
+      var CHUNKLEN = CHUNKDATA.length;
+
+      testUpdate +=
+        "n:1000\n" +
+        "i:" + LISTNAME + "\n" +
+        "s:" + SUB_CHUNKNUM + ":" + HASHLEN + ":" + CHUNKLEN + "\n" +
+        CHUNKDATA;
+    }
+
+    classifierHelper._updatesToCleanup =
+      classifierHelper._updatesToCleanup.filter((v) => {
+        return updateData.indexOf(v) == -1;
+      });
 
-    testUpdate +=
-      "n:1000\n" +
-      "i:" + LISTNAME + "\n" +
-      "s:" + SUB_CHUNKNUM + ":" + HASHLEN + ":" + CHUNKLEN + "\n" +
-      CHUNKDATA;
-  }
+    classifierHelper._update(testUpdate, resolve, reject);
+  });
+};
 
-  classifierHelper._updatesToCleanup =
-    classifierHelper._updatesToCleanup.filter((v) => {
-      return updateData.indexOf(v) == -1;
-    });
+// This API is used to expire all add/sub chunks we have updated
+// by using addUrlToDB and removeUrlFromDB.
+classifierHelper.resetDB = function() {
+  return new Promise(function(resolve, reject) {
+    var testUpdate = "";
+    for (var update of classifierHelper._updatesToCleanup) {
+      if (testUpdate.includes(update.db))
+        continue;
 
-  classifierHelper._update(testUpdate, onsuccess, onerror);
+      testUpdate +=
+        "n:1000\n" +
+        "i:" + update.db + "\n" +
+        "ad:" + ADD_CHUNKNUM + "\n" +
+        "sd:" + SUB_CHUNKNUM + "\n"
+    }
+
+    classifierHelper._update(testUpdate, resolve, reject);
+  });
 };
 
 classifierHelper._update = function(testUpdate, onsuccess, onerror) {
   // Queue the task if there is still an on-going update
   classifierHelper._updates.push({"data": testUpdate,
                                   "onsuccess": onsuccess,
                                   "onerror": onerror});
   if (classifierHelper._updates.length != 1) {
     return;
   }
 
-  classifierCommonScript.sendAsyncMessage("doUpdate", { testUpdate });
+  gScript.sendAsyncMessage("doUpdate", { testUpdate });
 };
 
 classifierHelper._updateSuccess = function() {
   var update = classifierHelper._updates.shift();
   update.onsuccess();
 
   if (classifierHelper._updates.length) {
     var testUpdate = classifierHelper._updates[0].data;
-    classifierCommonScript.sendAsyncMessage("doUpdate", { testUpdate });
+    gScript.sendAsyncMessage("doUpdate", { testUpdate });
   }
 };
 
 classifierHelper._updateError = function(errorCode) {
   var update = classifierHelper._updates.shift();
   update.onerror(errorCode);
 
   if (classifierHelper._updates.length) {
     var testUpdate = classifierHelper._updates[0].data;
-    classifierCommonScript.sendAsyncMessage("doUpdate", { testUpdate });
+    gScript.sendAsyncMessage("doUpdate", { testUpdate });
   }
 };
 
 classifierHelper._setup = function() {
-  classifierCommonScript.addMessageListener("updateSuccess", classifierHelper._updateSuccess);
-  classifierCommonScript.addMessageListener("updateError", classifierHelper._updateError);
+  gScript.addMessageListener("updateSuccess", classifierHelper._updateSuccess);
+  gScript.addMessageListener("updateError", classifierHelper._updateError);
 
   // cleanup will be called at end of each testcase to remove all the urls added to database.
   SimpleTest.registerCleanupFunction(classifierHelper._cleanup);
 };
 
 classifierHelper._cleanup = function() {
   if (!classifierHelper._updatesToCleanup) {
     return Promise.resolve();
   }
 
-  return new Promise(function(resolve, reject) {
-    classifierHelper.removeUrlFromDB(classifierHelper._updatesToCleanup, resolve, reject);
-  });
+  return classifierHelper.resetDB();
 };
 
 classifierHelper._setup();

--- a/toolkit/components/url-classifier/tests/mochitest/test_classifier.html
+++ b/toolkit/components/url-classifier/tests/mochitest/test_classifier.html
@@ -44,17 +44,21 @@ function updateError(errorCode) {
   // Abort test.
   SimpleTest.finish();
 }
 
 SpecialPowers.pushPrefEnv(
   {"set" : [["urlclassifier.malwareTable", "test-malware-simple,test-unwanted-simple"],
             ["urlclassifier.phishTable", "test-phish-simple"]]},
   function() {
-    classifierHelper.addUrlToDB(testData, updateSuccess, updateError);
+    classifierHelper.addUrlToDB(testData)
+      .then(updateSuccess)
+      .catch(err => {
+        updateError(err);
+      });
   });
 
 </script>
 
 </pre>
 <iframe id="testFrame" onload=""></iframe>
 </body>
 </html>

--- a/toolkit/components/url-classifier/tests/mochitest/test_classifier_worker.html
+++ b/toolkit/components/url-classifier/tests/mochitest/test_classifier_worker.html
@@ -51,17 +51,21 @@ function updateError(errorCode) {
   // Abort test.
   SimpleTest.finish();
 };
 
 SpecialPowers.pushPrefEnv(
   {"set" : [["urlclassifier.malwareTable", "test-malware-simple,test-unwanted-simple"],
             ["urlclassifier.phishTable", "test-phish-simple"]]},
   function() {
-    classifierHelper.addUrlToDB(testData, updateSuccess, updateError);
+    classifierHelper.addUrlToDB(testData)
+      .then(updateSuccess)
+      .catch(err => {
+        updateError(err);
+      });
   });
 
 window.addEventListener("message", onmessage, false);
 
 SimpleTest.waitForExplicitFinish();
 
 </script>
 

--- a/toolkit/components/url-classifier/tests/mochitest/test_classify_track.html
+++ b/toolkit/components/url-classifier/tests/mochitest/test_classify_track.html
@@ -112,29 +112,28 @@
     });
   }
 
   function cleanup() {
     SpecialPowers.clearUserPref(PREF);
   }
 
   function addMalewareUrlToDB() {
-    return new Promise(function(resolve, reject) {
-      var testData = [
-        { url: "malware.example.com/",
-          db: "test-malware-simple"
-        }
-      ];
+    var testData = [
+      { url: "malware.example.com/",
+        db: "test-malware-simple"
+      }
+    ];
 
-      classifierHelper.addUrlToDB(testData, resolve, function() {
-        ok(false, "Couldn't update classifier. Error code: " + errorCode);
+    return classifierHelper.addUrlToDB(testData)
+      .catch(function(err) {
+        ok(false, "Couldn't update classifier. Error code: " + err);
         // Abort test.
         SimpleTest.finish();
       });
-    });
   }
 
   function runTest() {
     Promise.resolve()
       .then(addMalewareUrlToDB)
       .then(testValidTrack)
       .then(testBlacklistTrackSafebrowsingOff)
       .then(testBlacklistTrackSafebrowsingOn)