--- a/toolkit/components/satchel/.eslintrc.js
+++ b/toolkit/components/satchel/.eslintrc.js
@@ -1,12 +1,14 @@
 "use strict";
 
 module.exports = {
   rules: {
+    "mozilla/var-only-at-top-level": "error",
+
     curly: ["error", "all"],
     indent: ["error", 2, {
       SwitchCase: 1,
       CallExpression: {
         arguments: "first",
       },
       FunctionExpression: {
         parameters: "first",

--- a/toolkit/components/satchel/formSubmitListener.js
+++ b/toolkit/components/satchel/formSubmitListener.js
@@ -6,17 +6,17 @@
 
 (function() {
 const { classes: Cc, interfaces: Ci, utils: Cu, results: Cr } = Components;
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/PrivateBrowsingUtils.jsm");
 
-var satchelFormListener = {
+let satchelFormListener = {
   QueryInterface: XPCOMUtils.generateQI([
     Ci.nsIFormSubmitObserver,
     Ci.nsIObserver,
     Ci.nsISupportsWeakReference
   ]),
 
   debug: true,
   enabled: true,

--- a/toolkit/components/satchel/test/satchel_common.js
+++ b/toolkit/components/satchel/test/satchel_common.js
@@ -8,23 +8,23 @@ var gPopupShownExpected = false;
 var gPopupShownListener;
 var gLastAutoCompleteResults;
 var gChromeScript;
 
 /*
  * Returns the element with the specified |name| attribute.
  */
 function $_(formNum, name) {
-  var form = document.getElementById("form" + formNum);
+  let form = document.getElementById("form" + formNum);
   if (!form) {
     ok(false, "$_ couldn't find requested form " + formNum);
     return null;
   }
 
-  var element = form.elements.namedItem(name);
+  let element = form.elements.namedItem(name);
   if (!element) {
     ok(false, "$_ couldn't find requested element " + name);
     return null;
   }
 
   // Note that namedItem is a bit stupid, and will prefer an
   // |id| attribute over a |name| attribute when looking for
   // the element.
@@ -35,26 +35,26 @@ function $_(formNum, name) {
   }
 
   return element;
 }
 
 // Mochitest gives us a sendKey(), but it's targeted to a specific element.
 // This basically sends an untargeted key event, to whatever's focused.
 function doKey(aKey, modifier) {
-  var keyName = "DOM_VK_" + aKey.toUpperCase();
-  var key = SpecialPowers.Ci.nsIDOMKeyEvent[keyName];
+  let keyName = "DOM_VK_" + aKey.toUpperCase();
+  let key = SpecialPowers.Ci.nsIDOMKeyEvent[keyName];
 
   // undefined --> null
   if (!modifier) {
     modifier = null;
   }
 
   // Window utils for sending fake key events.
-  var wutils = SpecialPowers.getDOMWindowUtils(window);
+  let wutils = SpecialPowers.getDOMWindowUtils(window);
 
   if (wutils.sendKeyEvent("keydown", key, 0, modifier)) {
     wutils.sendKeyEvent("keypress", key, 0, modifier);
   }
   wutils.sendKeyEvent("keyup", key, 0, modifier);
 }
 
 function registerPopupShownListener(listener) {
@@ -65,24 +65,24 @@ function registerPopupShownListener(list
   gPopupShownListener = listener;
 }
 
 function getMenuEntries() {
   if (!gLastAutoCompleteResults) {
     throw new Error("no autocomplete results");
   }
 
-  var results = gLastAutoCompleteResults;
+  let results = gLastAutoCompleteResults;
   gLastAutoCompleteResults = null;
   return results;
 }
 
 function checkArrayValues(actualValues, expectedValues, msg) {
   is(actualValues.length, expectedValues.length, "Checking array values: " + msg);
-  for (var i = 0; i < expectedValues.length; i++) {
+  for (let i = 0; i < expectedValues.length; i++) {
     is(actualValues[i], expectedValues[i], msg + " Checking array entry #" + i);
   }
 }
 
 var checkObserver = {
   verifyStack: [],
   callback: null,
 
@@ -113,41 +113,41 @@ var checkObserver = {
     // more. Here it is assumed that for every entry satchel saves or modifies, a
     // message is sent.
     //
     // We don't actually check the content of the message, but just that the right
     // quantity of messages is received.
     // - if there are too few messages, test will time out
     // - if there are too many messages, test will error out here
     //
-    var expected = this.verifyStack.shift();
+    let expected = this.verifyStack.shift();
 
     countEntries(expected.name, expected.value,
                  function(num) {
                    ok(num > 0, expected.message);
                    if (checkObserver.verifyStack.length == 0) {
-                     var callback = checkObserver.callback;
+                     let callback = checkObserver.callback;
                      checkObserver.callback = null;
                      callback();
                    }
                  });
   }
 };
 
 function checkForSave(name, value, message) {
   checkObserver.verifyStack.push({ name, value, message });
 }
 
 function getFormSubmitButton(formNum) {
-  var form = $("form" + formNum); // by id, not name
+  let form = $("form" + formNum); // by id, not name
   ok(form != null, "getting form " + formNum);
 
   // we can't just call form.submit(), because that doesn't seem to
   // invoke the form onsubmit handler.
-  var button = form.firstChild;
+  let button = form.firstChild;
   while (button && button.type != "submit") { button = button.nextSibling; }
   ok(button != null, "getting form submit button");
 
   return button;
 }
 
 // Count the number of entries with the given name and value, and call then(number)
 // when done. If name or value is null, then the value of that field does not matter.
@@ -257,17 +257,17 @@ function promiseACShown() {
     gPopupShownListener = ({ results }) => {
       gPopupShownExpected = false;
       resolve(results);
     };
   });
 }
 
 function satchelCommonSetup() {
-  var chromeURL = SimpleTest.getTestFileURL("parent_utils.js");
+  let chromeURL = SimpleTest.getTestFileURL("parent_utils.js");
   gChromeScript = SpecialPowers.loadChromeScript(chromeURL);
   gChromeScript.addMessageListener("onpopupshown", ({ results }) => {
     gLastAutoCompleteResults = results;
     if (gPopupShownListener) {
       gPopupShownListener({results});
     }
   });
 

--- a/toolkit/components/satchel/test/subtst_privbrowsing.html
+++ b/toolkit/components/satchel/test/subtst_privbrowsing.html
@@ -1,17 +1,17 @@
 <html>
 <head>
   <meta charset=UTF-8>
   <title>Subtest for bug 472396</title>
   <script>
   function submitForm() {
     if (location.search.indexOf("field") == -1) {
-      var form  = document.getElementById("form");
-      var field = document.getElementById("field");
+      let form  = document.getElementById("form");
+      let field = document.getElementById("field");
       field.value = "value";
       form.submit();
     }
   }
   </script>
 </head>
 <body onload="submitForm();">
   <h2>Subtest for bug 472396</h2>

--- a/toolkit/components/satchel/test/test_bug_787624.html
+++ b/toolkit/components/satchel/test/test_bug_787624.html
@@ -57,31 +57,31 @@ Form History Layout test: form field aut
 var resolvePopupShownListener;
 registerPopupShownListener(() => resolvePopupShownListener());
 
 function waitForNextPopup() {
   return new Promise(resolve => { resolvePopupShownListener = resolve; });
 }
 
 add_task(async function test_popup_not_move_input() {
-  var input = $_(1, "field1");
-  var rect = input.getBoundingClientRect();
+  let input = $_(1, "field1");
+  let rect = input.getBoundingClientRect();
 
   await new Promise(resolve => updateFormHistory([
     { op: "remove" },
     { op: "add", fieldname: "field1", value: "value1" },
     { op: "add", fieldname: "field1", value: "value2" },
   ], resolve));
 
   let popupShown = waitForNextPopup();
   input.focus();
   doKey("down");
   await popupShown;
 
-  var newRect = input.getBoundingClientRect();
+  let newRect = input.getBoundingClientRect();
   is(newRect.left, rect.left,
      "autocomplete popup does not disturb the input position");
   is(newRect.top, rect.top,
      "autocomplete popup does not disturb the input position");
 });
 
 </script>
 </pre>

--- a/toolkit/components/satchel/test/test_datalist_with_caching.html
+++ b/toolkit/components/satchel/test/test_datalist_with_caching.html
@@ -29,17 +29,17 @@ Form History test: form field autocomple
 </div>
 
 <pre id="test">
 <script class="testbody" type="text/javascript">
 /* import-globals-from ../../../../testing/mochitest/tests/SimpleTest/EventUtils.js */
 /* import-globals-from ../../../../testing/mochitest/tests/SimpleTest/SpawnTask.js */
 /* import-globals-from satchel_common.js */
 
-var input = $_(1, "field1");
+let input = $_(1, "field1");
 
 function setupFormHistory(aCallback) {
   updateFormHistory([
     { op: "remove" },
     { op: "add", fieldname: "field1", value: "Sec" },
   ], () => {
     spawn_task(aCallback);
   });
@@ -52,17 +52,17 @@ function setForm(value) {
 
 // Restore the form to the default state.
 function restoreForm() {
   setForm("");
 }
 
 // Check for expected form data.
 function checkForm(expectedValue) {
-  var formID = input.parentNode.id;
+  let formID = input.parentNode.id;
   is(input.value, expectedValue, "Checking " + formID + " input");
 }
 
 SimpleTest.waitForExplicitFinish();
 
 var expectingPopup = null;
 
 function expectPopup() {
@@ -88,19 +88,19 @@ function waitForMenuChange(expectedCount
   return new Promise(resolve => {
     notifyMenuChanged(expectedCount, null, resolve);
   });
 }
 
 registerPopupShownListener(popupShownListener);
 
 function checkMenuEntries(expectedValues) {
-  var actualValues = getMenuEntries();
+  let actualValues = getMenuEntries();
   is(actualValues.length, expectedValues.length, testNum + " Checking length of expected menu");
-  for (var i = 0; i < expectedValues.length; i++) {
+  for (let i = 0; i < expectedValues.length; i++) {
     is(actualValues[i], expectedValues[i], testNum + " Checking menu entry #" + i);
   }
 }
 
 async function runTests() {
   testNum++;
   restoreForm();
   doKey("down");

--- a/toolkit/components/satchel/test/test_form_autocomplete.html
+++ b/toolkit/components/satchel/test/test_form_autocomplete.html
@@ -196,17 +196,17 @@ function setForm(value) {
 
 // Restore the form to the default state.
 function restoreForm() {
   setForm("");
 }
 
 // Check for expected form data.
 function checkForm(expectedValue) {
-  var formID = input.parentNode.id;
+  let formID = input.parentNode.id;
   is(input.value, expectedValue, "Checking " + formID + " input");
 }
 
 var testNum = 0;
 var expectingPopup = false;
 
 function expectPopup() {
   info("expecting popup for test " + testNum);
@@ -1048,19 +1048,19 @@ function waitForScroll() {
   }, false);
 }
 
 function waitForMenuChange(expectedCount, expectedFirstValue) {
   notifyMenuChanged(expectedCount, expectedFirstValue, runTest);
 }
 
 function checkMenuEntries(expectedValues, testNumber) {
-  var actualValues = getMenuEntries();
+  let actualValues = getMenuEntries();
   is(actualValues.length, expectedValues.length, testNumber + " Checking length of expected menu");
-  for (var i = 0; i < expectedValues.length; i++) {
+  for (let i = 0; i < expectedValues.length; i++) {
     is(actualValues[i], expectedValues[i], testNumber + " Checking menu entry #" + i);
   }
 }
 
 function startTest() {
   setupFormHistory(function() {
     runTest();
   });

--- a/toolkit/components/satchel/test/test_form_autocomplete_with_list.html
+++ b/toolkit/components/satchel/test/test_form_autocomplete_with_list.html
@@ -65,17 +65,17 @@ function setForm(value) {
 
 // Restore the form to the default state.
 function restoreForm() {
   setForm("");
 }
 
 // Check for expected form data.
 function checkForm(expectedValue) {
-  var formID = input.parentNode.id;
+  let formID = input.parentNode.id;
   is(input.value, expectedValue, "Checking " + formID + " input");
 }
 
 var testNum = 0;
 var prevValue;
 var expectingPopup = false;
 
 function expectPopup() {
@@ -101,16 +101,17 @@ registerPopupShownListener(popupShownLis
 * This is a bit hacky, as many operations happen asynchronously.
 * Various mechanisms call runTests as a result of operations:
 *   - set expectingPopup to true, and the next test will occur when the autocomplete popup is shown
 *   - call waitForMenuChange(x) to run the next test when the autocomplete popup
 *     to have x items in it
 */
 function runTest() {
   testNum++;
+  let datalist;
 
   info("Starting test #" + testNum);
 
   switch (testNum) {
     case 1:
       // Make sure initial form is empty.
       checkForm("");
       // Trigger autocomplete popup
@@ -323,18 +324,18 @@ function runTest() {
     // Test dynamic updates.
     // For some reasons, when there is an update of the list, the selection is
     // lost so we need to go down like if we were at the beginning of the list
     // again.
     case 200:
       // Removing the second element while on the first then going down and
       // push enter. Value should be one from the third suggesion.
       doKey("down");
-      var datalist = document.getElementById("suggest");
-      var toRemove = datalist.children[1];
+      datalist = document.getElementById("suggest");
+      let toRemove = datalist.children[1];
       datalist.removeChild(toRemove);
 
       SimpleTest.executeSoon(function() {
         doKey("down");
         doKey("down");
         doKey("return");
         checkForm("final");
 
@@ -346,17 +347,17 @@ function runTest() {
       });
       break;
 
     case 201:
       // Adding an attribute after the first one while on the first then going
       // down and push enter. Value should be the on from the new suggestion.
       doKey("down");
       datalist = document.getElementById("suggest");
-      var added = new Option("Foo");
+      let added = new Option("Foo");
       datalist.insertBefore(added, datalist.children[1]);
       waitForMenuChange(4);
       break;
 
     case 202:
       doKey("down");
       doKey("down");
       doKey("return");
@@ -483,19 +484,19 @@ function runTest() {
   }
 }
 
 function waitForMenuChange(expectedCount) {
   notifyMenuChanged(expectedCount, null, runTest);
 }
 
 function checkMenuEntries(expectedValues, testNumber) {
-  var actualValues = getMenuEntries();
+  let actualValues = getMenuEntries();
   is(actualValues.length, expectedValues.length, testNumber + " Checking length of expected menu");
-  for (var i = 0; i < expectedValues.length; i++) {
+  for (let i = 0; i < expectedValues.length; i++) {
     is(actualValues[i], expectedValues[i], testNumber + " Checking menu entry #" + i);
   }
 }
 
 function startTest() {
   setupFormHistory(runTest);
 }
 

--- a/toolkit/components/satchel/test/test_form_submission.html
+++ b/toolkit/components/satchel/test/test_form_submission.html
@@ -309,17 +309,17 @@ function startTest() {
                           "012345678901234567890123456789012345678901234567890123456789012345678" +
                           "901234567890123456789012345678901234567890123456789012345678901234567" +
                           "89012345678901234567890123456789012345678901234567890";
   $_(12, "test1").value = " ";
   $_(13, "test1").value = "dontSaveThis";
   $_(14, "test1").type  = "password";
   $_(14, "test1").value = "dontSaveThis";
 
-  var testData = ccNumbers.valid16;
+  let testData = ccNumbers.valid16;
   for (let i = 0; i != testData.length; i++) {
     $_(15, "test" + (i + 1)).value = testData[i];
   }
 
   testData = ccNumbers.valid15;
   for (let i = 0; i != testData.length; i++) {
     $_(16, "test" + (i + 1)).value = testData[i];
   }
@@ -345,17 +345,17 @@ function startTest() {
   testData = ccNumbers.invalid15;
   for (let i = 0; i != testData.length; i++) {
     $_(108, "test8_" + (i + 1)).value = testData[i];
   }
 
   $_(109, "test9").value = "savedValue";
 
   // submit the first form.
-  var button = getFormSubmitButton(1);
+  let button = getFormSubmitButton(1);
   button.click();
 }
 
 
 // Called by each form's onsubmit handler.
 function checkSubmit(formNum) {
   ok(true, "form " + formNum + " submitted");
   numSubmittedForms++;
@@ -461,26 +461,26 @@ function submitForm(formNum) {
   // chain of submits will happen recursively since the submit is dispatched
   // immediately.
   //
   // This in itself is fine, but if there are errors in the code, mochitests
   // will in some cases give you "server too busy", which is hard to debug!
   //
   setTimeout(function() {
     checkObserver.waitForChecks(function() {
-      var nextFormNum = formNum == 22 ? 100 : (formNum + 1);
+      let nextFormNum = formNum == 22 ? 100 : (formNum + 1);
 
       // Submit the next form. Special cases are Forms 21 and 100, which happen
       // from an HTTPS domain in an iframe.
       if (nextFormNum == 100) {
         ok(true, "submitting iframe test " + nextFormNum);
         SpecialPowers.wrap(document.getElementById("iframe").contentWindow)
         .wrappedJSObject.clickButton(nextFormNum);
       } else {
-        var button = getFormSubmitButton(nextFormNum);
+        let button = getFormSubmitButton(nextFormNum);
         button.click();
       }
     });
   }, 0);
 
   return false; // cancel current form submission
 }
 

--- a/toolkit/components/satchel/test/test_form_submission_cap.html
+++ b/toolkit/components/satchel/test/test_form_submission_cap.html
@@ -33,33 +33,33 @@ function checkInitialState() {
   countEntries(null, null,
                function(num) {
                  ok(!num, "checking for initially empty storage");
                  startTest();
                });
 }
 
 function startTest() {
-  var form = document.getElementById("form1");
+  let form = document.getElementById("form1");
   for (let i = 1; i <= numInputFields; i++) {
-    var newField = document.createElement("input");
+    let newField = document.createElement("input");
     newField.setAttribute("type", "text");
     newField.setAttribute("name", "test" + i);
     form.appendChild(newField);
   }
 
   // Fill in values for the various fields. We could just set the <input>'s
   // value attribute, but we don't save default form values (and we want to
   // ensure unsaved values are because of autocomplete=off or whatever).
   for (let i = 1; i <= numInputFields; i++) {
     $_(1, "test" + i).value = i;
   }
 
   // submit the first form.
-  var button = getFormSubmitButton(1);
+  let button = getFormSubmitButton(1);
   button.click();
 }
 
 
 // Called by each form's onsubmit handler.
 function checkSubmit(formNum) {
   ok(true, "form " + formNum + " submitted");
   numSubmittedForms++;

--- a/toolkit/components/satchel/test/test_form_submission_cap2.html
+++ b/toolkit/components/satchel/test/test_form_submission_cap2.html
@@ -137,17 +137,17 @@ function checkInitialState() {
 
 function startTest() {
   // Fill in values for the various fields. We could just set the <input>'s
   // value attribute, but we don't save default form values (and we want to
   // ensure unsaved values are because of autocomplete=off or whatever).
   $_(1, "test" + numInputFields).value = numInputFields + " changed";
 
   // submit the first form.
-  var button = getFormSubmitButton(1);
+  let button = getFormSubmitButton(1);
   button.click();
 }
 
 // Make sure that the first (numInputFields - 1) were not saved (as they were not changed).
 // Call done() when finished.
 function checkCountEntries(formNum, index, done) {
   countEntries("test" + index, index,
                function(num) {

--- a/toolkit/components/satchel/test/test_popup_direction.html
+++ b/toolkit/components/satchel/test/test_popup_direction.html
@@ -27,17 +27,17 @@ Test for Popup Direction
 var resolvePopupShownListener;
 registerPopupShownListener(() => resolvePopupShownListener());
 
 function waitForNextPopup() {
   return new Promise(resolve => { resolvePopupShownListener = resolve; });
 }
 
 add_task(async function test_popup_direction() {
-  var input = $_(1, "field1");
+  let input = $_(1, "field1");
 
   await new Promise(resolve => updateFormHistory([
     { op: "remove" },
     { op: "add", fieldname: "field1", value: "value1" },
     { op: "add", fieldname: "field1", value: "value2" },
   ], resolve));
 
   for (let direction of ["ltr", "rtl"]) {

--- a/toolkit/components/satchel/test/unit/head_satchel.js
+++ b/toolkit/components/satchel/test/unit/head_satchel.js
@@ -17,20 +17,20 @@ var dirSvc = Cc["@mozilla.org/file/direc
 
 // Send the profile-after-change notification to the form history component to ensure
 // that it has been initialized.
 var formHistoryStartup = Cc["@mozilla.org/satchel/form-history-startup;1"]
                          .getService(Ci.nsIObserver);
 formHistoryStartup.observe(null, "profile-after-change", null);
 
 function getDBVersion(dbfile) {
-  var ss = Cc["@mozilla.org/storage/service;1"]
+  let ss = Cc["@mozilla.org/storage/service;1"]
              .getService(Ci.mozIStorageService);
-  var dbConnection = ss.openDatabase(dbfile);
-  var version = dbConnection.schemaVersion;
+  let dbConnection = ss.openDatabase(dbfile);
+  let version = dbConnection.schemaVersion;
   dbConnection.close();
 
   return version;
 }
 
 const isGUID = /[A-Za-z0-9\+\/]{16}/;
 
 // Find form history entries.
@@ -47,17 +47,17 @@ function searchEntries(terms, params, it
       }
     }
   });
 }
 
 // Count the number of entries with the given name and value, and call then(number)
 // when done. If name or value is null, then the value of that field does not matter.
 function countEntries(name, value, then) {
-  var obj = {};
+  let obj = {};
   if (name !== null) {
     obj.fieldname = name;
   }
   if (value !== null) {
     obj.value = value;
   }
 
   let count = 0;
@@ -71,17 +71,17 @@ function countEntries(name, value, then)
         then(count);
       }
     }
   });
 }
 
 // Perform a single form history update and call then() when done.
 function updateEntry(op, name, value, then) {
-  var obj = { op };
+  let obj = { op };
   if (name !== null) {
     obj.fieldname = name;
   }
   if (value !== null) {
     obj.value = value;
   }
   updateFormHistory(obj, then);
 }

--- a/toolkit/components/satchel/test/unit/test_async_expire.js
+++ b/toolkit/components/satchel/test/unit/test_async_expire.js
@@ -46,18 +46,18 @@ function run_test() {
 function next_test() {
   iter.next();
 }
 
 function* tests() {
   Services.obs.addObserver(TestObserver, "satchel-storage-changed", true);
 
   // ===== test init =====
-  var testfile = do_get_file("asyncformhistory_expire.sqlite");
-  var profileDir = do_get_profile();
+  let testfile = do_get_file("asyncformhistory_expire.sqlite");
+  let profileDir = do_get_profile();
 
   // Cleanup from any previous tests or failures.
   dbFile = profileDir.clone();
   dbFile.append("formhistory.sqlite");
   if (dbFile.exists()) {
     dbFile.remove(false);
   }
 
@@ -75,17 +75,17 @@ function* tests() {
   do_check_eq(CURRENT_SCHEMA, FormHistory.schemaVersion);
 
   // Add a new entry
   yield countEntries("name-C", "value-C", checkNotExists);
   yield addEntry("name-C", "value-C", next_test);
   yield countEntries("name-C", "value-C", checkExists);
 
   // Update some existing entries to have ages relative to when the test runs.
-  var now = 1000 * Date.now();
+  let now = 1000 * Date.now();
   let updateLastUsed = function updateLastUsedFn(results, age) {
     let lastUsed = now - age * 24 * PR_HOURS;
 
     let changes = [ ];
     for (let r = 0; r < results.length; r++) {
       changes.push({ op: "update", lastUsed, guid: results[r].guid });
     }
 

--- a/toolkit/components/satchel/test/unit/test_autocomplete.js
+++ b/toolkit/components/satchel/test/unit/test_autocomplete.js
@@ -8,55 +8,55 @@ var testnum = 0;
 var fac;
 var prefs;
 
 var numRecords, timeGroupingSize, now;
 
 const DEFAULT_EXPIRE_DAYS = 180;
 
 function padLeft(number, length) {
-  var str = number + "";
+  let str = number + "";
   while (str.length < length) {
     str = "0" + str;
   }
   return str;
 }
 
 function getFormExpiryDays() {
   if (prefs.prefHasUserValue("browser.formfill.expire_days")) {
     return prefs.getIntPref("browser.formfill.expire_days");
   }
   return DEFAULT_EXPIRE_DAYS;
 }
 
 function run_test() {
   // ===== test init =====
-  var testfile = do_get_file("formhistory_autocomplete.sqlite");
-  var profileDir = dirSvc.get("ProfD", Ci.nsIFile);
+  let testfile = do_get_file("formhistory_autocomplete.sqlite");
+  let profileDir = dirSvc.get("ProfD", Ci.nsIFile);
 
   // Cleanup from any previous tests or failures.
-  var destFile = profileDir.clone();
+  let destFile = profileDir.clone();
   destFile.append("formhistory.sqlite");
   if (destFile.exists()) {
     destFile.remove(false);
   }
 
   testfile.copyTo(profileDir, "formhistory.sqlite");
 
   fac = Cc["@mozilla.org/satchel/form-autocomplete;1"].getService(Ci.nsIFormAutoComplete);
   prefs = Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefBranch);
 
   timeGroupingSize = prefs.getIntPref("browser.formfill.timeGroupingSize") * 1000 * 1000;
 
   run_next_test();
 }
 
 add_test(function test0() {
-  var maxTimeGroupings = prefs.getIntPref("browser.formfill.maxTimeGroupings");
-  var bucketSize = prefs.getIntPref("browser.formfill.bucketSize");
+  let maxTimeGroupings = prefs.getIntPref("browser.formfill.maxTimeGroupings");
+  let bucketSize = prefs.getIntPref("browser.formfill.bucketSize");
 
   // ===== Tests with constant timesUsed and varying lastUsed date =====
   // insert 2 records per bucket to check alphabetical sort within
   now = 1000 * Date.now();
   numRecords = Math.ceil(maxTimeGroupings / bucketSize) * 2;
 
   let changes = [ ];
   for (let i = 0; i < numRecords; i += 2) {

--- a/toolkit/components/satchel/test/unit/test_db_update_v4.js
+++ b/toolkit/components/satchel/test/unit/test_db_update_v4.js
@@ -10,21 +10,21 @@ function run_test() {
   do_test_pending();
   iter = next_test();
   iter.next();
 }
 
 function* next_test() {
   try {
   // ===== test init =====
-    var testfile = do_get_file("formhistory_v3.sqlite");
-    var profileDir = dirSvc.get("ProfD", Ci.nsIFile);
+    let testfile = do_get_file("formhistory_v3.sqlite");
+    let profileDir = dirSvc.get("ProfD", Ci.nsIFile);
 
     // Cleanup from any previous tests or failures.
-    var destFile = profileDir.clone();
+    let destFile = profileDir.clone();
     destFile.append("formhistory.sqlite");
     if (destFile.exists()) {
       destFile.remove(false);
     }
 
     testfile.copyTo(profileDir, "formhistory.sqlite");
     do_check_eq(3, getDBVersion(testfile));
 

--- a/toolkit/components/satchel/test/unit/test_db_update_v4b.js
+++ b/toolkit/components/satchel/test/unit/test_db_update_v4b.js
@@ -10,21 +10,21 @@ function run_test() {
   do_test_pending();
   iter = next_test();
   iter.next();
 }
 
 function* next_test() {
   try {
   // ===== test init =====
-    var testfile = do_get_file("formhistory_v3v4.sqlite");
-    var profileDir = dirSvc.get("ProfD", Ci.nsIFile);
+    let testfile = do_get_file("formhistory_v3v4.sqlite");
+    let profileDir = dirSvc.get("ProfD", Ci.nsIFile);
 
     // Cleanup from any previous tests or failures.
-    var destFile = profileDir.clone();
+    let destFile = profileDir.clone();
     destFile.append("formhistory.sqlite");
     if (destFile.exists()) {
       destFile.remove(false);
     }
 
     testfile.copyTo(profileDir, "formhistory.sqlite");
     do_check_eq(3, getDBVersion(testfile));
 

--- a/toolkit/components/satchel/test/unit/test_db_update_v999a.js
+++ b/toolkit/components/satchel/test/unit/test_db_update_v999a.js
@@ -18,25 +18,25 @@ function run_test() {
   iter.next();
 }
 
 function next_test() {
   iter.next();
 }
 
 function* tests() {
-  var testnum = 0;
+  let testnum = 0;
 
   try {
     // ===== test init =====
-    var testfile = do_get_file("formhistory_v999a.sqlite");
-    var profileDir = dirSvc.get("ProfD", Ci.nsIFile);
+    let testfile = do_get_file("formhistory_v999a.sqlite");
+    let profileDir = dirSvc.get("ProfD", Ci.nsIFile);
 
     // Cleanup from any previous tests or failures.
-    var destFile = profileDir.clone();
+    let destFile = profileDir.clone();
     destFile.append("formhistory.sqlite");
     if (destFile.exists()) {
       destFile.remove(false);
     }
 
     testfile.copyTo(profileDir, "formhistory.sqlite");
     do_check_eq(999, getDBVersion(testfile));
 

--- a/toolkit/components/satchel/test/unit/test_db_update_v999b.js
+++ b/toolkit/components/satchel/test/unit/test_db_update_v999b.js
@@ -18,31 +18,31 @@ function run_test() {
   iter.next();
 }
 
 function next_test() {
   iter.next();
 }
 
 function* tests() {
-  var testnum = 0;
+  let testnum = 0;
 
   try {
     // ===== test init =====
-    var testfile = do_get_file("formhistory_v999b.sqlite");
-    var profileDir = dirSvc.get("ProfD", Ci.nsIFile);
+    let testfile = do_get_file("formhistory_v999b.sqlite");
+    let profileDir = dirSvc.get("ProfD", Ci.nsIFile);
 
     // Cleanup from any previous tests or failures.
-    var destFile = profileDir.clone();
+    let destFile = profileDir.clone();
     destFile.append("formhistory.sqlite");
     if (destFile.exists()) {
       destFile.remove(false);
     }
 
-    var bakFile = profileDir.clone();
+    let bakFile = profileDir.clone();
     bakFile.append("formhistory.sqlite.corrupt");
     if (bakFile.exists()) {
       bakFile.remove(false);
     }
 
     testfile.copyTo(profileDir, "formhistory.sqlite");
     do_check_eq(999, getDBVersion(testfile));
 

--- a/toolkit/components/satchel/test/unit/test_history_api.js
+++ b/toolkit/components/satchel/test/unit/test_history_api.js
@@ -45,17 +45,17 @@ function checkTimeDeleted(guid, checkFun
       handleCompletion() {
         stmt.finalize();
       }
     });
   });
 }
 
 function promiseUpdateEntry(op, name, value) {
-  var change = { op };
+  let change = { op };
   if (name !== null) {
     change.fieldname = name;
   }
   if (value !== null) {
     change.value = value;
   }
   return promiseUpdate(change);
 }
@@ -102,21 +102,21 @@ function promiseCountEntries(name, value
 }
 
 add_task(async function() {
   let oldSupportsDeletedTable = FormHistory._supportsDeletedTable;
   FormHistory._supportsDeletedTable = true;
 
   try {
   // ===== test init =====
-    var testfile = do_get_file("formhistory_apitest.sqlite");
-    var profileDir = dirSvc.get("ProfD", Ci.nsIFile);
+    let testfile = do_get_file("formhistory_apitest.sqlite");
+    let profileDir = dirSvc.get("ProfD", Ci.nsIFile);
 
     // Cleanup from any previous tests or failures.
-    var destFile = profileDir.clone();
+    let destFile = profileDir.clone();
     destFile.append("formhistory.sqlite");
     if (destFile.exists()) {
       destFile.remove(false);
     }
 
     testfile.copyTo(profileDir, "formhistory.sqlite");
 
     function checkExists(num) { do_check_true(num > 0); }

--- a/toolkit/components/satchel/test/unit/test_notify.js
+++ b/toolkit/components/satchel/test/unit/test_notify.js
@@ -1,19 +1,19 @@
 /*
  * Test suite for satchel notifications
  *
  * Tests notifications dispatched when modifying form history.
  *
  */
 
-var expectedNotification;
-var expectedData;
+let expectedNotification;
+let expectedData;
 
-var TestObserver = {
+let TestObserver = {
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver, Ci.nsISupportsWeakReference]),
 
   observe(subject, topic, data) {
     do_check_eq(topic, "satchel-storage-changed");
     do_check_eq(data, expectedNotification);
 
     switch (data) {
       case "formhistory-add":
@@ -28,47 +28,47 @@ var TestObserver = {
         do_throw("Unhandled notification: " + data + " / " + topic);
     }
 
     expectedNotification = null;
     expectedData = null;
   }
 };
 
-var testIterator = null;
+let testIterator = null;
 
 function run_test() {
   do_test_pending();
   testIterator = run_test_steps();
   testIterator.next();
 }
 
 function next_test() {
   testIterator.next();
 }
 
 function* run_test_steps() {
-  var testnum = 0;
-  var testdesc = "Setup of test form history entries";
+  let testnum = 0;
+  let testdesc = "Setup of test form history entries";
 
   try {
-    var entry1 = ["entry1", "value1"];
+    let entry1 = ["entry1", "value1"];
 
     /* ========== 1 ========== */
     testnum = 1;
     testdesc = "Initial connection to storage module";
 
     yield updateEntry("remove", null, null, next_test);
     yield countEntries(null, null, function(num) {
       do_check_false(num, "Checking initial DB is empty");
       next_test();
     });
 
     // Add the observer
-    var os = Cc["@mozilla.org/observer-service;1"].getService(Ci.nsIObserverService);
+    let os = Cc["@mozilla.org/observer-service;1"].getService(Ci.nsIObserverService);
     os.addObserver(TestObserver, "satchel-storage-changed");
 
     /* ========== 2 ========== */
     testnum++;
     testdesc = "addEntry";
 
     expectedNotification = "formhistory-add";
     expectedData = entry1;