--- a/browser/components/migration/ChromeMigrationUtils.jsm
+++ b/browser/components/migration/ChromeMigrationUtils.jsm
@@ -1,20 +1,18 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 "use strict";
 
 this.EXPORTED_SYMBOLS = ["ChromeMigrationUtils"];
 
 const { classes: Cc, interfaces: Ci, results: Cr, utils: Cu } = Components;
-const FILE_INPUT_STREAM_CID = "@mozilla.org/network/file-input-stream;1";
 
 Cu.import("resource://gre/modules/AppConstants.jsm");
-Cu.import("resource://gre/modules/FileUtils.jsm");
 Cu.import("resource://gre/modules/NetUtil.jsm");
 Cu.import("resource://gre/modules/osfile.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 
 this.ChromeMigrationUtils = {
   _chromeUserDataPath: null,
 
@@ -32,17 +30,20 @@ this.ChromeMigrationUtils = {
   // }
   _extensionLocaleStrings: {},
 
   /**
    * Get all extensions installed in a specific profile.
    * @param {String} profileId - A Chrome user profile ID. For example, "Profile 1".
    * @returns {Array} All installed Chrome extensions information.
    */
-  async getExtensionList(profileId = this.getLastUsedProfileId()) {
+  async getExtensionList(profileId) {
+    if (profileId === undefined) {
+      profileId = await this.getLastUsedProfileId();
+    }
     let path = this.getExtensionPath(profileId);
     let iterator = new OS.File.DirectoryIterator(path);
     let extensionList = [];
     await iterator.forEach(async entry => {
       if (entry.isDir) {
         let extensionInformation = await this.getExtensionInformation(entry.name, profileId);
         if (extensionInformation) {
           extensionList.push(extensionInformation);
@@ -53,17 +54,20 @@ this.ChromeMigrationUtils = {
   },
 
   /**
    * Get information of a specific Chrome extension.
    * @param {String} extensionId - The extension ID.
    * @param {String} profileId - The user profile's ID.
    * @retruns {Object} The Chrome extension information.
    */
-  async getExtensionInformation(extensionId, profileId = this.getLastUsedProfileId()) {
+  async getExtensionInformation(extensionId, profileId) {
+    if (profileId === undefined) {
+      profileId = await this.getLastUsedProfileId();
+    }
     let extensionInformation = null;
     try {
       let manifestPath = this.getExtensionPath(profileId);
       manifestPath = OS.Path.join(manifestPath, extensionId);
       // If there are multiple sub-directories in the extension directory,
       // read the files in the latest directory.
       let directories = await this._getSortedByVersionSubDirectoryNames(manifestPath);
       if (!directories[0]) {
@@ -146,50 +150,44 @@ this.ChromeMigrationUtils = {
   },
 
   /**
    * Check that a specific extension is installed or not.
    * @param {String} extensionId - The extension ID.
    * @param {String} profileId - The user profile's ID.
    * @returns {Boolean} Return true if the extension is installed otherwise return false.
    */
-  async isExtensionInstalled(extensionId, profileId = this.getLastUsedProfileId()) {
+  async isExtensionInstalled(extensionId, profileId) {
+    if (profileId === undefined) {
+      profileId = await this.getLastUsedProfileId();
+    }
     let extensionPath = this.getExtensionPath(profileId);
     let isInstalled = await OS.File.exists(OS.Path.join(extensionPath, extensionId));
     return isInstalled;
   },
 
   /**
    * Get the last used user profile's ID.
    * @returns {String} The last used user profile's ID.
    */
-  getLastUsedProfileId() {
-    let localState = this.getLocalState();
+  async getLastUsedProfileId() {
+    let localState = await this.getLocalState();
     return localState ? localState.profile.last_used : "Default";
   },
 
   /**
    * Get the local state file content.
    * @returns {Object} The JSON-based content.
    */
-  getLocalState() {
-    let localStateFile = new FileUtils.File(this.getChromeUserDataPath());
-    localStateFile.append("Local State");
-    if (!localStateFile.exists())
-      throw new Error("Chrome's 'Local State' file does not exist.");
-    if (!localStateFile.isReadable())
-      throw new Error("Chrome's 'Local State' file could not be read.");
-
+  async getLocalState() {
     let localState = null;
     try {
-      let fstream = Cc[FILE_INPUT_STREAM_CID].createInstance(Ci.nsIFileInputStream);
-      fstream.init(localStateFile, -1, 0, 0);
-      let inputStream = NetUtil.readInputStreamToString(fstream, fstream.available(),
-                                                        { charset: "UTF-8" });
-      localState = JSON.parse(inputStream);
+      let localStatePath = OS.Path.join(this.getChromeUserDataPath(), "Local State");
+      let localStateJson = await OS.File.read(localStatePath, { encoding: "utf-8" });
+      localState = JSON.parse(localStateJson);
     } catch (ex) {
       Cu.reportError(ex);
       throw ex;
     }
     return localState;
   },
 
   /**

--- a/browser/components/migration/ChromeProfileMigrator.js
+++ b/browser/components/migration/ChromeProfileMigrator.js
@@ -3,29 +3,26 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 const { classes: Cc, interfaces: Ci, results: Cr, utils: Cu } = Components;
 
-const FILE_INPUT_STREAM_CID = "@mozilla.org/network/file-input-stream;1";
-
 const S100NS_FROM1601TO1970 = 0x19DB1DED53E8000;
 const S100NS_PER_MS = 10;
 
 const AUTH_TYPE = {
   SCHEME_HTML: 0,
   SCHEME_BASIC: 1,
   SCHEME_DIGEST: 2,
 };
 
 Cu.import("resource://gre/modules/AppConstants.jsm");
-Cu.import("resource://gre/modules/FileUtils.jsm");
 Cu.import("resource://gre/modules/NetUtil.jsm");
 Cu.import("resource://gre/modules/osfile.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource:///modules/ChromeMigrationUtils.jsm");
 Cu.import("resource:///modules/MigrationUtils.jsm");
 
 XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils",
@@ -87,147 +84,159 @@ function convertBookmarks(items, errorAc
       Cu.reportError(ex);
       errorAccumulator(ex);
     }
   }
   return itemsToInsert;
 }
 
 function ChromeProfileMigrator() {
-  let path = ChromeMigrationUtils.getDataPath("Chrome");
-  let chromeUserDataFolder = new FileUtils.File(path);
-  this._chromeUserDataFolder = chromeUserDataFolder.exists() ?
-    chromeUserDataFolder : null;
+  this._chromeUserDataPathSuffix = "Chrome";
 }
 
 ChromeProfileMigrator.prototype = Object.create(MigratorPrototype);
 
+ChromeProfileMigrator.prototype._getChromeUserDataPathIfExists = async function() {
+  if (this._chromeUserDataPath) {
+    return this._chromeUserDataPath;
+  }
+  let path = ChromeMigrationUtils.getDataPath(this._chromeUserDataPathSuffix);
+  let exists = await OS.File.exists(path);
+  if (exists) {
+    this._chromeUserDataPath = path;
+  } else {
+    this._chromeUserDataPath = null;
+  }
+  return this._chromeUserDataPath;
+};
+
 ChromeProfileMigrator.prototype.getResources =
-  function Chrome_getResources(aProfile) {
-    if (this._chromeUserDataFolder) {
-      let profileFolder = this._chromeUserDataFolder.clone();
-      profileFolder.append(aProfile.id);
-      if (profileFolder.exists()) {
-        let possibleResources = [
+  async function Chrome_getResources(aProfile) {
+    let chromeUserDataPath = await this._getChromeUserDataPathIfExists();
+    if (chromeUserDataPath) {
+      let profileFolder = OS.Path.join(chromeUserDataPath, aProfile.id);
+      if (await OS.File.exists(profileFolder)) {
+        let possibleResourcePromises = [
           GetBookmarksResource(profileFolder),
           GetHistoryResource(profileFolder),
           GetCookiesResource(profileFolder),
         ];
         if (AppConstants.platform == "win") {
-          possibleResources.push(GetWindowsPasswordsResource(profileFolder));
+          possibleResourcePromises.push(GetWindowsPasswordsResource(profileFolder));
         }
+        let possibleResources = await Promise.all(possibleResourcePromises);
         return possibleResources.filter(r => r != null);
       }
     }
     return [];
   };
 
 ChromeProfileMigrator.prototype.getLastUsedDate =
-  function Chrome_getLastUsedDate() {
-    let datePromises = this.sourceProfiles.map(profile => {
-      let basePath = OS.Path.join(this._chromeUserDataFolder.path, profile.id);
-      let fileDatePromises = ["Bookmarks", "History", "Cookies"].map(leafName => {
+  async function Chrome_getLastUsedDate() {
+    let sourceProfiles = await this.getSourceProfiles();
+    let chromeUserDataPath = await this._getChromeUserDataPathIfExists();
+    if (!chromeUserDataPath) {
+      return new Date(0);
+    }
+    let datePromises = sourceProfiles.map(async profile => {
+      let basePath = OS.Path.join(chromeUserDataPath, profile.id);
+      let fileDatePromises = ["Bookmarks", "History", "Cookies"].map(async leafName => {
         let path = OS.Path.join(basePath, leafName);
-        return OS.File.stat(path).catch(() => null).then(info => {
-          return info ? info.lastModificationDate : 0;
-        });
+        let info = await OS.File.stat(path).catch(() => null);
+        return info ? info.lastModificationDate : 0;
       });
-      return Promise.all(fileDatePromises).then(dates => {
-        return Math.max.apply(Math, dates);
-      });
+      let dates = await Promise.all(fileDatePromises);
+      return Math.max(...dates);
     });
-    return Promise.all(datePromises).then(dates => {
-      dates.push(0);
-      return new Date(Math.max.apply(Math, dates));
-    });
+    let datesOuter = await Promise.all(datePromises);
+    datesOuter.push(0);
+    return new Date(Math.max(...datesOuter));
   };
 
 ChromeProfileMigrator.prototype.getSourceProfiles =
   async function Chrome_getSourceProfiles() {
     if ("__sourceProfiles" in this)
       return this.__sourceProfiles;
 
-    if (!this._chromeUserDataFolder)
+    let chromeUserDataPath = await this._getChromeUserDataPathIfExists();
+    if (!chromeUserDataPath)
       return [];
 
     let profiles = [];
     try {
-      let info_cache = ChromeMigrationUtils.getLocalState().profile.info_cache;
+      let localState = await ChromeMigrationUtils.getLocalState();
+      let info_cache = localState.profile.info_cache;
       for (let profileFolderName in info_cache) {
-        let profileFolder = this._chromeUserDataFolder.clone();
-        profileFolder.append(profileFolderName);
         profiles.push({
           id: profileFolderName,
           name: info_cache[profileFolderName].name || profileFolderName,
         });
       }
     } catch (e) {
       Cu.reportError("Error detecting Chrome profiles: " + e);
       // If we weren't able to detect any profiles above, fallback to the Default profile.
-      let defaultProfileFolder = this._chromeUserDataFolder.clone();
-      defaultProfileFolder.append("Default");
-      if (defaultProfileFolder.exists()) {
+      let defaultProfilePath = OS.Path.join(chromeUserDataPath, "Default");
+      if (await OS.File.exists(defaultProfilePath)) {
         profiles = [{
           id: "Default",
           name: "Default",
         }];
       }
     }
 
+    let profileResources = await Promise.all(profiles.map(async profile => ({
+      profile,
+      resources: await this.getResources(profile),
+    })));
+
     // Only list profiles from which any data can be imported
-    this.__sourceProfiles = profiles.filter(function(profile) {
-      let resources = this.getResources(profile);
+    this.__sourceProfiles = profileResources.filter(({resources}) => {
       return resources && resources.length > 0;
-    }, this);
+    }, this).map(({profile}) => profile);
     return this.__sourceProfiles;
   };
 
 ChromeProfileMigrator.prototype.getSourceHomePageURL =
   async function Chrome_getSourceHomePageURL() {
-    let prefsFile = this._chromeUserDataFolder.clone();
-    prefsFile.append("Preferences");
-    if (prefsFile.exists()) {
-      // XXX reading and parsing JSON is synchronous.
-      let fstream = Cc[FILE_INPUT_STREAM_CID].
-                    createInstance(Ci.nsIFileInputStream);
-      fstream.init(prefsFile, -1, 0, 0);
+    let chromeUserDataPath = await this._getChromeUserDataPathIfExists();
+    if (!chromeUserDataPath)
+      return "";
+    let prefsPath = OS.Path.join(chromeUserDataPath, "Preferences");
+    if (await OS.File.exists(prefsPath)) {
       try {
-        return JSON.parse(
-          NetUtil.readInputStreamToString(fstream, fstream.available(),
-                                          { charset: "UTF-8" })
-            ).homepage;
+        let json = await OS.File.read(prefsPath, {encoding: "UTF-8"});
+        return JSON.parse(json).homepage;
       } catch (e) {
         Cu.reportError("Error parsing Chrome's preferences file: " + e);
       }
     }
     return "";
   };
 
 Object.defineProperty(ChromeProfileMigrator.prototype, "sourceLocked", {
   get: function Chrome_sourceLocked() {
     // There is an exclusive lock on some SQLite databases. Assume they are locked for now.
     return true;
   },
 });
 
-function GetBookmarksResource(aProfileFolder) {
-  let bookmarksFile = aProfileFolder.clone();
-  bookmarksFile.append("Bookmarks");
-  if (!bookmarksFile.exists())
+async function GetBookmarksResource(aProfileFolder) {
+  let bookmarksPath = OS.Path.join(aProfileFolder, "Bookmarks");
+  if (!(await OS.File.exists(bookmarksPath)))
     return null;
 
   return {
     type: MigrationUtils.resourceTypes.BOOKMARKS,
 
     migrate(aCallback) {
       return (async function() {
         let gotErrors = false;
         let errorGatherer = function() { gotErrors = true; };
         // Parse Chrome bookmark file that is JSON format
-        let bookmarkJSON = await OS.File.read(bookmarksFile.path, {encoding: "UTF-8"});
+        let bookmarkJSON = await OS.File.read(bookmarksPath, {encoding: "UTF-8"});
         let roots = JSON.parse(bookmarkJSON).roots;
 
         // Importing bookmark bar items
         if (roots.bookmark_bar.children &&
             roots.bookmark_bar.children.length > 0) {
           // Toolbar
           let parentGuid = PlacesUtils.bookmarks.toolbarGuid;
           let bookmarks = convertBookmarks(roots.bookmark_bar.children, errorGatherer);
@@ -254,20 +263,19 @@ function GetBookmarksResource(aProfileFo
           throw new Error("The migration included errors.");
         }
       })().then(() => aCallback(true),
               () => aCallback(false));
     },
   };
 }
 
-function GetHistoryResource(aProfileFolder) {
-  let historyFile = aProfileFolder.clone();
-  historyFile.append("History");
-  if (!historyFile.exists())
+async function GetHistoryResource(aProfileFolder) {
+  let historyPath = OS.Path.join(aProfileFolder, "History");
+  if (!(await OS.File.exists(historyPath)))
     return null;
 
   return {
     type: MigrationUtils.resourceTypes.HISTORY,
 
     migrate(aCallback) {
       (async function() {
         const MAX_AGE_IN_DAYS = Services.prefs.getIntPref("browser.migrate.chrome.history.maxAgeInDays");
@@ -278,17 +286,17 @@ function GetHistoryResource(aProfileFold
           let maxAge = dateToChromeTime(Date.now() - MAX_AGE_IN_DAYS * 24 * 60 * 60 * 1000);
           query += " AND last_visit_time > " + maxAge;
         }
         if (LIMIT) {
           query += " ORDER BY last_visit_time DESC LIMIT " + LIMIT;
         }
 
         let rows =
-          await MigrationUtils.getRowsFromDBWithoutLocks(historyFile.path, "Chrome history", query);
+          await MigrationUtils.getRowsFromDBWithoutLocks(historyPath, "Chrome history", query);
         let places = [];
         for (let row of rows) {
           try {
             // if having typed_count, we changes transition type to typed.
             let transType = PlacesUtils.history.TRANSITION_LINK;
             if (row.getResultByName("typed_count") > 0)
               transType = PlacesUtils.history.TRANSITION_TYPED;
 
@@ -326,28 +334,27 @@ function GetHistoryResource(aProfileFold
               ex => {
                 Cu.reportError(ex);
                 aCallback(false);
               });
     },
   };
 }
 
-function GetCookiesResource(aProfileFolder) {
-  let cookiesFile = aProfileFolder.clone();
-  cookiesFile.append("Cookies");
-  if (!cookiesFile.exists())
+async function GetCookiesResource(aProfileFolder) {
+  let cookiesPath = OS.Path.join(aProfileFolder, "Cookies");
+  if (!(await OS.File.exists(cookiesPath)))
     return null;
 
   return {
     type: MigrationUtils.resourceTypes.COOKIES,
 
     async migrate(aCallback) {
       // We don't support decrypting cookies yet so only import plaintext ones.
-      let rows = await MigrationUtils.getRowsFromDBWithoutLocks(cookiesFile.path, "Chrome cookies",
+      let rows = await MigrationUtils.getRowsFromDBWithoutLocks(cookiesPath, "Chrome cookies",
        `SELECT host_key, name, value, path, expires_utc, secure, httponly, encrypted_value
         FROM cookies
         WHERE length(encrypted_value) = 0`).catch(ex => {
           Cu.reportError(ex);
           aCallback(false);
         });
       // If the promise was rejected we will have already called aCallback,
       // so we can just return here.
@@ -378,27 +385,26 @@ function GetCookiesResource(aProfileFold
           Cu.reportError(e);
         }
       }
       aCallback(true);
     },
   };
 }
 
-function GetWindowsPasswordsResource(aProfileFolder) {
-  let loginFile = aProfileFolder.clone();
-  loginFile.append("Login Data");
-  if (!loginFile.exists())
+async function GetWindowsPasswordsResource(aProfileFolder) {
+  let loginPath = OS.Path.join(aProfileFolder, "Login Data");
+  if (!(await OS.File.exists(loginPath)))
     return null;
 
   return {
     type: MigrationUtils.resourceTypes.PASSWORDS,
 
     async migrate(aCallback) {
-      let rows = await MigrationUtils.getRowsFromDBWithoutLocks(loginFile.path, "Chrome passwords",
+      let rows = await MigrationUtils.getRowsFromDBWithoutLocks(loginPath, "Chrome passwords",
        `SELECT origin_url, action_url, username_element, username_value,
         password_element, password_value, signon_realm, scheme, date_created,
         times_used FROM logins WHERE blacklisted_by_user = 0`).catch(ex => {
           Cu.reportError(ex);
           aCallback(false);
         });
       // If the promise was rejected we will have already called aCallback,
       // so we can just return here.
@@ -463,36 +469,32 @@ ChromeProfileMigrator.prototype.classDes
 ChromeProfileMigrator.prototype.contractID = "@mozilla.org/profile/migrator;1?app=browser&type=chrome";
 ChromeProfileMigrator.prototype.classID = Components.ID("{4cec1de4-1671-4fc3-a53e-6c539dc77a26}");
 
 
 /**
  *  Chromium migration
  **/
 function ChromiumProfileMigrator() {
-  let path = ChromeMigrationUtils.getDataPath("Chromium");
-  let chromiumUserDataFolder = new FileUtils.File(path);
-  this._chromeUserDataFolder = chromiumUserDataFolder.exists() ? chromiumUserDataFolder : null;
+  this._chromeUserDataPathSuffix = "Chromium";
 }
 
 ChromiumProfileMigrator.prototype = Object.create(ChromeProfileMigrator.prototype);
 ChromiumProfileMigrator.prototype.classDescription = "Chromium Profile Migrator";
 ChromiumProfileMigrator.prototype.contractID = "@mozilla.org/profile/migrator;1?app=browser&type=chromium";
 ChromiumProfileMigrator.prototype.classID = Components.ID("{8cece922-9720-42de-b7db-7cef88cb07ca}");
 
 var componentsArray = [ChromeProfileMigrator, ChromiumProfileMigrator];
 
 /**
  * Chrome Canary
  * Not available on Linux
  **/
 function CanaryProfileMigrator() {
-  let path = ChromeMigrationUtils.getDataPath("Canary");
-  let chromeUserDataFolder = new FileUtils.File(path);
-  this._chromeUserDataFolder = chromeUserDataFolder.exists() ? chromeUserDataFolder : null;
+  this._chromeUserDataPathSuffix = "Canary";
 }
 CanaryProfileMigrator.prototype = Object.create(ChromeProfileMigrator.prototype);
 CanaryProfileMigrator.prototype.classDescription = "Chrome Canary Profile Migrator";
 CanaryProfileMigrator.prototype.contractID = "@mozilla.org/profile/migrator;1?app=browser&type=canary";
 CanaryProfileMigrator.prototype.classID = Components.ID("{4bf85aa5-4e21-46ca-825f-f9c51a5e8c76}");
 
 if (AppConstants.platform == "win" || AppConstants.platform == "macosx") {
   componentsArray.push(CanaryProfileMigrator);