Add m-esr52 at 52.6.0

12 files changed, 6298 insertions, 0 deletions

diff --git a/toolkit/components/jsdownloads/src/DownloadCore.jsm b/toolkit/components/jsdownloads/src/DownloadCore.jsm
new file mode 100644
index 000000000..d89dd5805
--- /dev/null
+++ b/toolkit/components/jsdownloads/src/DownloadCore.jsm
@@ -0,0 +1,2871 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* 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/. */
+
+/**
+ * This file includes the following constructors and global objects:
+ *
+ * Download
+ * Represents a single download, with associated state and actions.  This object
+ * is transient, though it can be included in a DownloadList so that it can be
+ * managed by the user interface and persisted across sessions.
+ *
+ * DownloadSource
+ * Represents the source of a download, for example a document or an URI.
+ *
+ * DownloadTarget
+ * Represents the target of a download, for example a file in the global
+ * downloads directory, or a file in the system temporary directory.
+ *
+ * DownloadError
+ * Provides detailed information about a download failure.
+ *
+ * DownloadSaver
+ * Template for an object that actually transfers the data for the download.
+ *
+ * DownloadCopySaver
+ * Saver object that simply copies the entire source file to the target.
+ *
+ * DownloadLegacySaver
+ * Saver object that integrates with the legacy nsITransfer interface.
+ *
+ * DownloadPDFSaver
+ * This DownloadSaver type creates a PDF file from the current document in a
+ * given window, specified using the windowRef property of the DownloadSource
+ * object associated with the download.
+ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "Download",
+  "DownloadSource",
+  "DownloadTarget",
+  "DownloadError",
+  "DownloadSaver",
+  "DownloadCopySaver",
+  "DownloadLegacySaver",
+  "DownloadPDFSaver",
+];
+
+// Globals
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+const Cr = Components.results;
+
+Cu.import("resource://gre/modules/Integration.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
+                                  "resource://gre/modules/FileUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
+                                  "resource://gre/modules/NetUtil.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "OS",
+                                  "resource://gre/modules/osfile.jsm")
+XPCOMUtils.defineLazyModuleGetter(this, "Promise",
+                                  "resource://gre/modules/Promise.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Services",
+                                  "resource://gre/modules/Services.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+                                  "resource://gre/modules/Task.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "PrivateBrowsingUtils",
+                                  "resource://gre/modules/PrivateBrowsingUtils.jsm");
+
+XPCOMUtils.defineLazyServiceGetter(this, "gDownloadHistory",
+           "@mozilla.org/browser/download-history;1",
+           Ci.nsIDownloadHistory);
+XPCOMUtils.defineLazyServiceGetter(this, "gExternalAppLauncher",
+           "@mozilla.org/uriloader/external-helper-app-service;1",
+           Ci.nsPIExternalAppLauncher);
+XPCOMUtils.defineLazyServiceGetter(this, "gExternalHelperAppService",
+           "@mozilla.org/uriloader/external-helper-app-service;1",
+           Ci.nsIExternalHelperAppService);
+XPCOMUtils.defineLazyServiceGetter(this, "gPrintSettingsService",
+           "@mozilla.org/gfx/printsettings-service;1",
+           Ci.nsIPrintSettingsService);
+
+Integration.downloads.defineModuleGetter(this, "DownloadIntegration",
+            "resource://gre/modules/DownloadIntegration.jsm");
+
+const BackgroundFileSaverStreamListener = Components.Constructor(
+      "@mozilla.org/network/background-file-saver;1?mode=streamlistener",
+      "nsIBackgroundFileSaver");
+
+/**
+ * Returns true if the given value is a primitive string or a String object.
+ */
+function isString(aValue) {
+  // We cannot use the "instanceof" operator reliably across module boundaries.
+  return (typeof aValue == "string") ||
+         (typeof aValue == "object" && "charAt" in aValue);
+}
+
+/**
+ * Serialize the unknown properties of aObject into aSerializable.
+ */
+function serializeUnknownProperties(aObject, aSerializable)
+{
+  if (aObject._unknownProperties) {
+    for (let property in aObject._unknownProperties) {
+      aSerializable[property] = aObject._unknownProperties[property];
+    }
+  }
+}
+
+/**
+ * Check for any unknown properties in aSerializable and preserve those in the
+ * _unknownProperties field of aObject. aFilterFn is called for each property
+ * name of aObject and should return true only for unknown properties.
+ */
+function deserializeUnknownProperties(aObject, aSerializable, aFilterFn)
+{
+  for (let property in aSerializable) {
+    if (aFilterFn(property)) {
+      if (!aObject._unknownProperties) {
+        aObject._unknownProperties = { };
+      }
+
+      aObject._unknownProperties[property] = aSerializable[property];
+    }
+  }
+}
+
+/**
+ * This determines the minimum time interval between updates to the number of
+ * bytes transferred, and is a limiting factor to the sequence of readings used
+ * in calculating the speed of the download.
+ */
+const kProgressUpdateIntervalMs = 400;
+
+// Download
+
+/**
+ * Represents a single download, with associated state and actions.  This object
+ * is transient, though it can be included in a DownloadList so that it can be
+ * managed by the user interface and persisted across sessions.
+ */
+this.Download = function ()
+{
+  this._deferSucceeded = Promise.defer();
+}
+
+this.Download.prototype = {
+  /**
+   * DownloadSource object associated with this download.
+   */
+  source: null,
+
+  /**
+   * DownloadTarget object associated with this download.
+   */
+  target: null,
+
+  /**
+   * DownloadSaver object associated with this download.
+   */
+  saver: null,
+
+  /**
+   * Indicates that the download never started, has been completed successfully,
+   * failed, or has been canceled.  This property becomes false when a download
+   * is started for the first time, or when a failed or canceled download is
+   * restarted.
+   */
+  stopped: true,
+
+  /**
+   * Indicates that the download has been completed successfully.
+   */
+  succeeded: false,
+
+  /**
+   * Indicates that the download has been canceled.  This property can become
+   * true, then it can be reset to false when a canceled download is restarted.
+   *
+   * This property becomes true as soon as the "cancel" method is called, though
+   * the "stopped" property might remain false until the cancellation request
+   * has been processed.  Temporary files or part files may still exist even if
+   * they are expected to be deleted, until the "stopped" property becomes true.
+   */
+  canceled: false,
+
+  /**
+   * When the download fails, this is set to a DownloadError instance indicating
+   * the cause of the failure.  If the download has been completed successfully
+   * or has been canceled, this property is null.  This property is reset to
+   * null when a failed download is restarted.
+   */
+  error: null,
+
+  /**
+   * Indicates the start time of the download.  When the download starts,
+   * this property is set to a valid Date object.  The default value is null
+   * before the download starts.
+   */
+  startTime: null,
+
+  /**
+   * Indicates whether this download's "progress" property is able to report
+   * partial progress while the download proceeds, and whether the value in
+   * totalBytes is relevant.  This depends on the saver and the download source.
+   */
+  hasProgress: false,
+
+  /**
+   * Progress percent, from 0 to 100.  Intermediate values are reported only if
+   * hasProgress is true.
+   *
+   * @note You shouldn't rely on this property being equal to 100 to determine
+   *       whether the download is completed.  You should use the individual
+   *       state properties instead.
+   */
+  progress: 0,
+
+  /**
+   * When hasProgress is true, indicates the total number of bytes to be
+   * transferred before the download finishes, that can be zero for empty files.
+   *
+   * When hasProgress is false, this property is always zero.
+   *
+   * @note This property may be different than the final file size on disk for
+   *       downloads that are encoded during the network transfer.  You can use
+   *       the "size" property of the DownloadTarget object to get the actual
+   *       size on disk once the download succeeds.
+   */
+  totalBytes: 0,
+
+  /**
+   * Number of bytes currently transferred.  This value starts at zero, and may
+   * be updated regardless of the value of hasProgress.
+   *
+   * @note You shouldn't rely on this property being equal to totalBytes to
+   *       determine whether the download is completed.  You should use the
+   *       individual state properties instead.  This property may not be
+   *       updated during the last part of the download.
+   */
+  currentBytes: 0,
+
+  /**
+   * Fractional number representing the speed of the download, in bytes per
+   * second.  This value is zero when the download is stopped, and may be
+   * updated regardless of the value of hasProgress.
+   */
+  speed: 0,
+
+  /**
+   * Indicates whether, at this time, there is any partially downloaded data
+   * that can be used when restarting a failed or canceled download.
+   *
+   * Even if the download has partial data on disk, hasPartialData will be false
+   * if that data cannot be used to restart the download. In order to determine
+   * if a part file is being used which contains partial data the
+   * Download.target.partFilePath should be checked.
+   *
+   * This property is relevant while the download is in progress, and also if it
+   * failed or has been canceled.  If the download has been completed
+   * successfully, this property is always false.
+   *
+   * Whether partial data can actually be retained depends on the saver and the
+   * download source, and may not be known before the download is started.
+   */
+  hasPartialData: false,
+
+  /**
+   * Indicates whether, at this time, there is any data that has been blocked.
+   * Since reputation blocking takes place after the download has fully
+   * completed a value of true also indicates 100% of the data is present.
+   */
+  hasBlockedData: false,
+
+  /**
+   * This can be set to a function that is called after other properties change.
+   */
+  onchange: null,
+
+  /**
+   * This tells if the user has chosen to open/run the downloaded file after
+   * download has completed.
+   */
+  launchWhenSucceeded: false,
+
+  /**
+   * This represents the MIME type of the download.
+   */
+  contentType: null,
+
+  /**
+   * This indicates the path of the application to be used to launch the file,
+   * or null if the file should be launched with the default application.
+   */
+  launcherPath: null,
+
+  /**
+   * Raises the onchange notification.
+   */
+  _notifyChange: function D_notifyChange() {
+    try {
+      if (this.onchange) {
+        this.onchange();
+      }
+    } catch (ex) {
+      Cu.reportError(ex);
+    }
+  },
+
+  /**
+   * The download may be stopped and restarted multiple times before it
+   * completes successfully. This may happen if any of the download attempts is
+   * canceled or fails.
+   *
+   * This property contains a promise that is linked to the current attempt, or
+   * null if the download is either stopped or in the process of being canceled.
+   * If the download restarts, this property is replaced with a new promise.
+   *
+   * The promise is resolved if the attempt it represents finishes successfully,
+   * and rejected if the attempt fails.
+   */
+  _currentAttempt: null,
+
+  /**
+   * Starts the download for the first time, or restarts a download that failed
+   * or has been canceled.
+   *
+   * Calling this method when the download has been completed successfully has
+   * no effect, and the method returns a resolved promise.  If the download is
+   * in progress, the method returns the same promise as the previous call.
+   *
+   * If the "cancel" method was called but the cancellation process has not
+   * finished yet, this method waits for the cancellation to finish, then
+   * restarts the download immediately.
+   *
+   * @note If you need to start a new download from the same source, rather than
+   *       restarting a failed or canceled one, you should create a separate
+   *       Download object with the same source as the current one.
+   *
+   * @return {Promise}
+   * @resolves When the download has finished successfully.
+   * @rejects JavaScript exception if the download failed.
+   */
+  start: function D_start()
+  {
+    // If the download succeeded, it's the final state, we have nothing to do.
+    if (this.succeeded) {
+      return Promise.resolve();
+    }
+
+    // If the download already started and hasn't failed or hasn't been
+    // canceled, return the same promise as the previous call, allowing the
+    // caller to wait for the current attempt to finish.
+    if (this._currentAttempt) {
+      return this._currentAttempt;
+    }
+
+    // While shutting down or disposing of this object, we prevent the download
+    // from returning to be in progress.
+    if (this._finalized) {
+      return Promise.reject(new DownloadError({
+                                message: "Cannot start after finalization."}));
+    }
+
+    if (this.error && this.error.becauseBlockedByReputationCheck) {
+      return Promise.reject(new DownloadError({
+                                message: "Cannot start after being blocked " +
+                                         "by a reputation check."}));
+    }
+
+    // Initialize all the status properties for a new or restarted download.
+    this.stopped = false;
+    this.canceled = false;
+    this.error = null;
+    this.hasProgress = false;
+    this.hasBlockedData = false;
+    this.progress = 0;
+    this.totalBytes = 0;
+    this.currentBytes = 0;
+    this.startTime = new Date();
+
+    // Create a new deferred object and an associated promise before starting
+    // the actual download.  We store it on the download as the current attempt.
+    let deferAttempt = Promise.defer();
+    let currentAttempt = deferAttempt.promise;
+    this._currentAttempt = currentAttempt;
+
+    // Restart the progress and speed calculations from scratch.
+    this._lastProgressTimeMs = 0;
+
+    // This function propagates progress from the DownloadSaver object, unless
+    // it comes in late from a download attempt that was replaced by a new one.
+    // If the cancellation process for the download has started, then the update
+    // is ignored.
+    function DS_setProgressBytes(aCurrentBytes, aTotalBytes, aHasPartialData)
+    {
+      if (this._currentAttempt == currentAttempt) {
+        this._setBytes(aCurrentBytes, aTotalBytes, aHasPartialData);
+      }
+    }
+
+    // This function propagates download properties from the DownloadSaver
+    // object, unless it comes in late from a download attempt that was
+    // replaced by a new one.  If the cancellation process for the download has
+    // started, then the update is ignored.
+    function DS_setProperties(aOptions)
+    {
+      if (this._currentAttempt != currentAttempt) {
+        return;
+      }
+
+      let changeMade = false;
+
+      for (let property of ["contentType", "progress", "hasPartialData",
+                            "hasBlockedData"]) {
+        if (property in aOptions && this[property] != aOptions[property]) {
+          this[property] = aOptions[property];
+          changeMade = true;
+        }
+      }
+
+      if (changeMade) {
+        this._notifyChange();
+      }
+    }
+
+    // Now that we stored the promise in the download object, we can start the
+    // task that will actually execute the download.
+    deferAttempt.resolve(Task.spawn(function* task_D_start() {
+      // Wait upon any pending operation before restarting.
+      if (this._promiseCanceled) {
+        yield this._promiseCanceled;
+      }
+      if (this._promiseRemovePartialData) {
+        try {
+          yield this._promiseRemovePartialData;
+        } catch (ex) {
+          // Ignore any errors, which are already reported by the original
+          // caller of the removePartialData method.
+        }
+      }
+
+      // In case the download was restarted while cancellation was in progress,
+      // but the previous attempt actually succeeded before cancellation could
+      // be processed, it is possible that the download has already finished.
+      if (this.succeeded) {
+        return;
+      }
+
+      try {
+        // Disallow download if parental controls service restricts it.
+        if (yield DownloadIntegration.shouldBlockForParentalControls(this)) {
+          throw new DownloadError({ becauseBlockedByParentalControls: true });
+        }
+
+        // Disallow download if needed runtime permissions have not been granted
+        // by user.
+        if (yield DownloadIntegration.shouldBlockForRuntimePermissions()) {
+          throw new DownloadError({ becauseBlockedByRuntimePermissions: true });
+        }
+
+        // We should check if we have been canceled in the meantime, after all
+        // the previous asynchronous operations have been executed and just
+        // before we call the "execute" method of the saver.
+        if (this._promiseCanceled) {
+          // The exception will become a cancellation in the "catch" block.
+          throw undefined;
+        }
+
+        // Execute the actual download through the saver object.
+        this._saverExecuting = true;
+        yield this.saver.execute(DS_setProgressBytes.bind(this),
+                                 DS_setProperties.bind(this));
+
+        // Now that the actual saving finished, read the actual file size on
+        // disk, that may be different from the amount of data transferred.
+        yield this.target.refresh();
+
+        // Check for the last time if the download has been canceled. This must
+        // be done right before setting the "stopped" property of the download,
+        // without any asynchronous operations in the middle, so that another
+        // cancellation request cannot start in the meantime and stay unhandled.
+        if (this._promiseCanceled) {
+          try {
+            yield OS.File.remove(this.target.path);
+          } catch (ex) {
+            Cu.reportError(ex);
+          }
+
+          this.target.exists = false;
+          this.target.size = 0;
+
+          // Cancellation exceptions will be changed in the catch block below.
+          throw new DownloadError();
+        }
+
+        // Update the status properties for a successful download.
+        this.progress = 100;
+        this.succeeded = true;
+        this.hasPartialData = false;
+      } catch (originalEx) {
+        // We may choose a different exception to propagate in the code below,
+        // or wrap the original one. We do this mutation in a different variable
+        // because of the "no-ex-assign" ESLint rule.
+        let ex = originalEx;
+
+        // Fail with a generic status code on cancellation, so that the caller
+        // is forced to actually check the status properties to see if the
+        // download was canceled or failed because of other reasons.
+        if (this._promiseCanceled) {
+          throw new DownloadError({ message: "Download canceled." });
+        }
+
+        // An HTTP 450 error code is used by Windows to indicate that a uri is
+        // blocked by parental controls. This will prevent the download from
+        // occuring, so an error needs to be raised. This is not performed
+        // during the parental controls check above as it requires the request
+        // to start.
+        if (this._blockedByParentalControls) {
+          ex = new DownloadError({ becauseBlockedByParentalControls: true });
+        }
+
+        // Update the download error, unless a new attempt already started. The
+        // change in the status property is notified in the finally block.
+        if (this._currentAttempt == currentAttempt || !this._currentAttempt) {
+          if (!(ex instanceof DownloadError)) {
+            let properties = {innerException: ex};
+
+            if (ex.message) {
+              properties.message = ex.message;
+            }
+
+            ex = new DownloadError(properties);
+          }
+
+          this.error = ex;
+        }
+        throw ex;
+      } finally {
+        // Any cancellation request has now been processed.
+        this._saverExecuting = false;
+        this._promiseCanceled = null;
+
+        // Update the status properties, unless a new attempt already started.
+        if (this._currentAttempt == currentAttempt || !this._currentAttempt) {
+          this._currentAttempt = null;
+          this.stopped = true;
+          this.speed = 0;
+          this._notifyChange();
+          if (this.succeeded) {
+            yield this._succeed();
+          }
+        }
+      }
+    }.bind(this)));
+
+    // Notify the new download state before returning.
+    this._notifyChange();
+    return currentAttempt;
+  },
+
+  /**
+   * Perform the actions necessary when a Download succeeds.
+   *
+   * @return {Promise}
+   * @resolves When the steps to take after success have completed.
+   * @rejects  JavaScript exception if any of the operations failed.
+   */
+  _succeed: Task.async(function* () {
+    yield DownloadIntegration.downloadDone(this);
+
+    this._deferSucceeded.resolve();
+
+    if (this.launchWhenSucceeded) {
+      this.launch().then(null, Cu.reportError);
+
+      // Always schedule files to be deleted at the end of the private browsing
+      // mode, regardless of the value of the pref.
+      if (this.source.isPrivate) {
+        gExternalAppLauncher.deleteTemporaryPrivateFileWhenPossible(
+                             new FileUtils.File(this.target.path));
+      } else if (Services.prefs.getBoolPref(
+                  "browser.helperApps.deleteTempFileOnExit")) {
+        gExternalAppLauncher.deleteTemporaryFileOnExit(
+                             new FileUtils.File(this.target.path));
+      }
+    }
+  }),
+
+  /**
+   * When a request to unblock the download is received, contains a promise
+   * that will be resolved when the unblock request is completed. This property
+   * will then continue to hold the promise indefinitely.
+   */
+  _promiseUnblock: null,
+
+  /**
+   * When a request to confirm the block of the download is received, contains
+   * a promise that will be resolved when cleaning up the download has
+   * completed. This property will then continue to hold the promise
+   * indefinitely.
+   */
+  _promiseConfirmBlock: null,
+
+  /**
+   * Unblocks a download which had been blocked by reputation.
+   *
+   * The file will be moved out of quarantine and the download will be
+   * marked as succeeded.
+   *
+   * @return {Promise}
+   * @resolves When the Download has been unblocked and succeeded.
+   * @rejects  JavaScript exception if any of the operations failed.
+   */
+  unblock: function() {
+    if (this._promiseUnblock) {
+      return this._promiseUnblock;
+    }
+
+    if (this._promiseConfirmBlock) {
+      return Promise.reject(new Error(
+        "Download block has been confirmed, cannot unblock."));
+    }
+
+    if (!this.hasBlockedData) {
+      return Promise.reject(new Error(
+        "unblock may only be called on Downloads with blocked data."));
+    }
+
+    this._promiseUnblock = Task.spawn(function* () {
+      try {
+        yield OS.File.move(this.target.partFilePath, this.target.path);
+        yield this.target.refresh();
+      } catch (ex) {
+        yield this.refresh();
+        this._promiseUnblock = null;
+        throw ex;
+      }
+
+      this.succeeded = true;
+      this.hasBlockedData = false;
+      this._notifyChange();
+      yield this._succeed();
+    }.bind(this));
+
+    return this._promiseUnblock;
+  },
+
+  /**
+   * Confirms that a blocked download should be cleaned up.
+   *
+   * If a download was blocked but retained on disk this method can be used
+   * to remove the file.
+   *
+   * @return {Promise}
+   * @resolves When the Download's data has been removed.
+   * @rejects  JavaScript exception if any of the operations failed.
+   */
+  confirmBlock: function() {
+    if (this._promiseConfirmBlock) {
+      return this._promiseConfirmBlock;
+    }
+
+    if (this._promiseUnblock) {
+      return Promise.reject(new Error(
+        "Download is being unblocked, cannot confirmBlock."));
+    }
+
+    if (!this.hasBlockedData) {
+      return Promise.reject(new Error(
+        "confirmBlock may only be called on Downloads with blocked data."));
+    }
+
+    this._promiseConfirmBlock = Task.spawn(function* () {
+      try {
+        yield OS.File.remove(this.target.partFilePath);
+      } catch (ex) {
+        yield this.refresh();
+        this._promiseConfirmBlock = null;
+        throw ex;
+      }
+
+      this.hasBlockedData = false;
+      this._notifyChange();
+    }.bind(this));
+
+    return this._promiseConfirmBlock;
+  },
+
+  /*
+   * Launches the file after download has completed. This can open
+   * the file with the default application for the target MIME type
+   * or file extension, or with a custom application if launcherPath
+   * is set.
+   *
+   * @return {Promise}
+   * @resolves When the instruction to launch the file has been
+   *           successfully given to the operating system. Note that
+   *           the OS might still take a while until the file is actually
+   *           launched.
+   * @rejects  JavaScript exception if there was an error trying to launch
+   *           the file.
+   */
+  launch: function () {
+    if (!this.succeeded) {
+      return Promise.reject(
+        new Error("launch can only be called if the download succeeded")
+      );
+    }
+
+    return DownloadIntegration.launchDownload(this);
+  },
+
+  /*
+   * Shows the folder containing the target file, or where the target file
+   * will be saved. This may be called at any time, even if the download
+   * failed or is currently in progress.
+   *
+   * @return {Promise}
+   * @resolves When the instruction to open the containing folder has been
+   *           successfully given to the operating system. Note that
+   *           the OS might still take a while until the folder is actually
+   *           opened.
+   * @rejects  JavaScript exception if there was an error trying to open
+   *           the containing folder.
+   */
+  showContainingDirectory: function D_showContainingDirectory() {
+    return DownloadIntegration.showContainingDirectory(this.target.path);
+  },
+
+  /**
+   * When a request to cancel the download is received, contains a promise that
+   * will be resolved when the cancellation request is processed.  When the
+   * request is processed, this property becomes null again.
+   */
+  _promiseCanceled: null,
+
+  /**
+   * True between the call to the "execute" method of the saver and the
+   * completion of the current download attempt.
+   */
+  _saverExecuting: false,
+
+  /**
+   * Cancels the download.
+   *
+   * The cancellation request is asynchronous.  Until the cancellation process
+   * finishes, temporary files or part files may still exist even if they are
+   * expected to be deleted.
+   *
+   * In case the download completes successfully before the cancellation request
+   * could be processed, this method has no effect, and it returns a resolved
+   * promise.  You should check the properties of the download at the time the
+   * returned promise is resolved to determine if the download was cancelled.
+   *
+   * Calling this method when the download has been completed successfully,
+   * failed, or has been canceled has no effect, and the method returns a
+   * resolved promise.  This behavior is designed for the case where the call
+   * to "cancel" happens asynchronously, and is consistent with the case where
+   * the cancellation request could not be processed in time.
+   *
+   * @return {Promise}
+   * @resolves When the cancellation process has finished.
+   * @rejects Never.
+   */
+  cancel: function D_cancel()
+  {
+    // If the download is currently stopped, we have nothing to do.
+    if (this.stopped) {
+      return Promise.resolve();
+    }
+
+    if (!this._promiseCanceled) {
+      // Start a new cancellation request.
+      let deferCanceled = Promise.defer();
+      this._currentAttempt.then(() => deferCanceled.resolve(),
+                                () => deferCanceled.resolve());
+      this._promiseCanceled = deferCanceled.promise;
+
+      // The download can already be restarted.
+      this._currentAttempt = null;
+
+      // Notify that the cancellation request was received.
+      this.canceled = true;
+      this._notifyChange();
+
+      // Execute the actual cancellation through the saver object, in case it
+      // has already started.  Otherwise, the cancellation will be handled just
+      // before the saver is started.
+      if (this._saverExecuting) {
+        this.saver.cancel();
+      }
+    }
+
+    return this._promiseCanceled;
+  },
+
+  /**
+   * Indicates whether any partially downloaded data should be retained, to use
+   * when restarting a failed or canceled download.  The default is false.
+   *
+   * Whether partial data can actually be retained depends on the saver and the
+   * download source, and may not be known before the download is started.
+   *
+   * To have any effect, this property must be set before starting the download.
+   * Resetting this property to false after the download has already started
+   * will not remove any partial data.
+   *
+   * If this property is set to true, care should be taken that partial data is
+   * removed before the reference to the download is discarded.  This can be
+   * done using the removePartialData or the "finalize" methods.
+   */
+  tryToKeepPartialData: false,
+
+  /**
+   * When a request to remove partially downloaded data is received, contains a
+   * promise that will be resolved when the removal request is processed.  When
+   * the request is processed, this property becomes null again.
+   */
+  _promiseRemovePartialData: null,
+
+  /**
+   * Removes any partial data kept as part of a canceled or failed download.
+   *
+   * If the download is not canceled or failed, this method has no effect, and
+   * it returns a resolved promise.  If the "cancel" method was called but the
+   * cancellation process has not finished yet, this method waits for the
+   * cancellation to finish, then removes the partial data.
+   *
+   * After this method has been called, if the tryToKeepPartialData property is
+   * still true when the download is restarted, partial data will be retained
+   * during the new download attempt.
+   *
+   * @return {Promise}
+   * @resolves When the partial data has been successfully removed.
+   * @rejects JavaScript exception if the operation could not be completed.
+   */
+  removePartialData: function ()
+  {
+    if (!this.canceled && !this.error) {
+      return Promise.resolve();
+    }
+
+    let promiseRemovePartialData = this._promiseRemovePartialData;
+
+    if (!promiseRemovePartialData) {
+      let deferRemovePartialData = Promise.defer();
+      promiseRemovePartialData = deferRemovePartialData.promise;
+      this._promiseRemovePartialData = promiseRemovePartialData;
+
+      deferRemovePartialData.resolve(
+        Task.spawn(function* task_D_removePartialData() {
+          try {
+            // Wait upon any pending cancellation request.
+            if (this._promiseCanceled) {
+              yield this._promiseCanceled;
+            }
+            // Ask the saver object to remove any partial data.
+            yield this.saver.removePartialData();
+            // For completeness, clear the number of bytes transferred.
+            if (this.currentBytes != 0 || this.hasPartialData) {
+              this.currentBytes = 0;
+              this.hasPartialData = false;
+              this._notifyChange();
+            }
+          } finally {
+            this._promiseRemovePartialData = null;
+          }
+        }.bind(this)));
+    }
+
+    return promiseRemovePartialData;
+  },
+
+  /**
+   * This deferred object contains a promise that is resolved as soon as this
+   * download finishes successfully, and is never rejected.  This property is
+   * initialized when the download is created, and never changes.
+   */
+  _deferSucceeded: null,
+
+  /**
+   * Returns a promise that is resolved as soon as this download finishes
+   * successfully, even if the download was stopped and restarted meanwhile.
+   *
+   * You can use this property for scheduling download completion actions in the
+   * current session, for downloads that are controlled interactively.  If the
+   * download is not controlled interactively, you should use the promise
+   * returned by the "start" method instead, to check for success or failure.
+   *
+   * @return {Promise}
+   * @resolves When the download has finished successfully.
+   * @rejects Never.
+   */
+  whenSucceeded: function D_whenSucceeded()
+  {
+    return this._deferSucceeded.promise;
+  },
+
+  /**
+   * Updates the state of a finished, failed, or canceled download based on the
+   * current state in the file system.  If the download is in progress or it has
+   * been finalized, this method has no effect, and it returns a resolved
+   * promise.
+   *
+   * This allows the properties of the download to be updated in case the user
+   * moved or deleted the target file or its associated ".part" file.
+   *
+   * @return {Promise}
+   * @resolves When the operation has completed.
+   * @rejects Never.
+   */
+  refresh: function ()
+  {
+    return Task.spawn(function* () {
+      if (!this.stopped || this._finalized) {
+        return;
+      }
+
+      if (this.succeeded) {
+        let oldExists = this.target.exists;
+        let oldSize = this.target.size;
+        yield this.target.refresh();
+        if (oldExists != this.target.exists || oldSize != this.target.size) {
+          this._notifyChange();
+        }
+        return;
+      }
+
+      // Update the current progress from disk if we retained partial data.
+      if ((this.hasPartialData || this.hasBlockedData) &&
+          this.target.partFilePath) {
+
+        try {
+          let stat = yield OS.File.stat(this.target.partFilePath);
+
+          // Ignore the result if the state has changed meanwhile.
+          if (!this.stopped || this._finalized) {
+            return;
+          }
+
+          // Update the bytes transferred and the related progress properties.
+          this.currentBytes = stat.size;
+          if (this.totalBytes > 0) {
+            this.hasProgress = true;
+            this.progress = Math.floor(this.currentBytes /
+                                           this.totalBytes * 100);
+          }
+        } catch (ex) {
+          if (!(ex instanceof OS.File.Error) || !ex.becauseNoSuchFile) {
+            throw ex;
+          }
+          // Ignore the result if the state has changed meanwhile.
+          if (!this.stopped || this._finalized) {
+            return;
+          }
+
+          this.hasBlockedData = false;
+          this.hasPartialData = false;
+        }
+
+        this._notifyChange();
+      }
+    }.bind(this)).then(null, Cu.reportError);
+  },
+
+  /**
+   * True if the "finalize" method has been called.  This prevents the download
+   * from starting again after having been stopped.
+   */
+  _finalized: false,
+
+  /**
+   * Ensures that the download is stopped, and optionally removes any partial
+   * data kept as part of a canceled or failed download.  After this method has
+   * been called, the download cannot be started again.
+   *
+   * This method should be used in place of "cancel" and removePartialData while
+   * shutting down or disposing of the download object, to prevent other callers
+   * from interfering with the operation.  This is required because cancellation
+   * and other operations are asynchronous.
+   *
+   * @param aRemovePartialData
+   *        Whether any partially downloaded data should be removed after the
+   *        download has been stopped.
+   *
+   * @return {Promise}
+   * @resolves When the operation has finished successfully.
+   * @rejects JavaScript exception if an error occurred while removing the
+   *          partially downloaded data.
+   */
+  finalize: function (aRemovePartialData)
+  {
+    // Prevents the download from starting again after having been stopped.
+    this._finalized = true;
+
+    if (aRemovePartialData) {
+      // Cancel the download, in case it is currently in progress, then remove
+      // any partially downloaded data.  The removal operation waits for
+      // cancellation to be completed before resolving the promise it returns.
+      this.cancel();
+      return this.removePartialData();
+    }
+    // Just cancel the download, in case it is currently in progress.
+    return this.cancel();
+  },
+
+  /**
+   * Indicates the time of the last progress notification, expressed as the
+   * number of milliseconds since January 1, 1970, 00:00:00 UTC.  This is zero
+   * until some bytes have actually been transferred.
+   */
+  _lastProgressTimeMs: 0,
+
+  /**
+   * Updates progress notifications based on the number of bytes transferred.
+   *
+   * The number of bytes transferred is not updated unless enough time passed
+   * since this function was last called.  This limits the computation load, in
+   * particular when the listeners update the user interface in response.
+   *
+   * @param aCurrentBytes
+   *        Number of bytes transferred until now.
+   * @param aTotalBytes
+   *        Total number of bytes to be transferred, or -1 if unknown.
+   * @param aHasPartialData
+   *        Indicates whether the partially downloaded data can be used when
+   *        restarting the download if it fails or is canceled.
+   */
+  _setBytes: function D_setBytes(aCurrentBytes, aTotalBytes, aHasPartialData) {
+    let changeMade = (this.hasPartialData != aHasPartialData);
+    this.hasPartialData = aHasPartialData;
+
+    // Unless aTotalBytes is -1, we can report partial download progress.  In
+    // this case, notify when the related properties changed since last time.
+    if (aTotalBytes != -1 && (!this.hasProgress ||
+                              this.totalBytes != aTotalBytes)) {
+      this.hasProgress = true;
+      this.totalBytes = aTotalBytes;
+      changeMade = true;
+    }
+
+    // Updating the progress and computing the speed require that enough time
+    // passed since the last update, or that we haven't started throttling yet.
+    let currentTimeMs = Date.now();
+    let intervalMs = currentTimeMs - this._lastProgressTimeMs;
+    if (intervalMs >= kProgressUpdateIntervalMs) {
+      // Don't compute the speed unless we started throttling notifications.
+      if (this._lastProgressTimeMs != 0) {
+        // Calculate the speed in bytes per second.
+        let rawSpeed = (aCurrentBytes - this.currentBytes) / intervalMs * 1000;
+        if (this.speed == 0) {
+          // When the previous speed is exactly zero instead of a fractional
+          // number, this can be considered the first element of the series.
+          this.speed = rawSpeed;
+        } else {
+          // Apply exponential smoothing, with a smoothing factor of 0.1.
+          this.speed = rawSpeed * 0.1 + this.speed * 0.9;
+        }
+      }
+
+      // Start throttling notifications only when we have actually received some
+      // bytes for the first time.  The timing of the first part of the download
+      // is not reliable, due to possible latency in the initial notifications.
+      // This also allows automated tests to receive and verify the number of
+      // bytes initially transferred.
+      if (aCurrentBytes > 0) {
+        this._lastProgressTimeMs = currentTimeMs;
+
+        // Update the progress now that we don't need its previous value.
+        this.currentBytes = aCurrentBytes;
+        if (this.totalBytes > 0) {
+          this.progress = Math.floor(this.currentBytes / this.totalBytes * 100);
+        }
+        changeMade = true;
+      }
+    }
+
+    if (changeMade) {
+      this._notifyChange();
+    }
+  },
+
+  /**
+   * Returns a static representation of the current object state.
+   *
+   * @return A JavaScript object that can be serialized to JSON.
+   */
+  toSerializable: function ()
+  {
+    let serializable = {
+      source: this.source.toSerializable(),
+      target: this.target.toSerializable(),
+    };
+
+    let saver = this.saver.toSerializable();
+    if (!serializable.source || !saver) {
+      // If we are unable to serialize either the source or the saver,
+      // we won't persist the download.
+      return null;
+    }
+
+    // Simplify the representation for the most common saver type.  If the saver
+    // is an object instead of a simple string, we can't simplify it because we
+    // need to persist all its properties, not only "type".  This may happen for
+    // savers of type "copy" as well as other types.
+    if (saver !== "copy") {
+      serializable.saver = saver;
+    }
+
+    if (this.error) {
+      serializable.errorObj = this.error.toSerializable();
+    }
+
+    if (this.startTime) {
+      serializable.startTime = this.startTime.toJSON();
+    }
+
+    // These are serialized unless they are false, null, or empty strings.
+    for (let property of kPlainSerializableDownloadProperties) {
+      if (this[property]) {
+        serializable[property] = this[property];
+      }
+    }
+
+    serializeUnknownProperties(this, serializable);
+
+    return serializable;
+  },
+
+  /**
+   * Returns a value that changes only when one of the properties of a Download
+   * object that should be saved into a file also change.  This excludes
+   * properties whose value doesn't usually change during the download lifetime.
+   *
+   * This function is used to determine whether the download should be
+   * serialized after a property change notification has been received.
+   *
+   * @return String representing the relevant download state.
+   */
+  getSerializationHash: function ()
+  {
+    // The "succeeded", "canceled", "error", and startTime properties are not
+    // taken into account because they all change before the "stopped" property
+    // changes, and are not altered in other cases.
+    return this.stopped + "," + this.totalBytes + "," + this.hasPartialData +
+           "," + this.contentType;
+  },
+};
+
+/**
+ * Defines which properties of the Download object are serializable.
+ */
+const kPlainSerializableDownloadProperties = [
+  "succeeded",
+  "canceled",
+  "totalBytes",
+  "hasPartialData",
+  "hasBlockedData",
+  "tryToKeepPartialData",
+  "launcherPath",
+  "launchWhenSucceeded",
+  "contentType",
+];
+
+/**
+ * Creates a new Download object from a serializable representation.  This
+ * function is used by the createDownload method of Downloads.jsm when a new
+ * Download object is requested, thus some properties may refer to live objects
+ * in place of their serializable representations.
+ *
+ * @param aSerializable
+ *        An object with the following fields:
+ *        {
+ *          source: DownloadSource object, or its serializable representation.
+ *                  See DownloadSource.fromSerializable for details.
+ *          target: DownloadTarget object, or its serializable representation.
+ *                  See DownloadTarget.fromSerializable for details.
+ *          saver: Serializable representation of a DownloadSaver object.  See
+ *                 DownloadSaver.fromSerializable for details.  If omitted,
+ *                 defaults to "copy".
+ *        }
+ *
+ * @return The newly created Download object.
+ */
+Download.fromSerializable = function (aSerializable) {
+  let download = new Download();
+  if (aSerializable.source instanceof DownloadSource) {
+    download.source = aSerializable.source;
+  } else {
+    download.source = DownloadSource.fromSerializable(aSerializable.source);
+  }
+  if (aSerializable.target instanceof DownloadTarget) {
+    download.target = aSerializable.target;
+  } else {
+    download.target = DownloadTarget.fromSerializable(aSerializable.target);
+  }
+  if ("saver" in aSerializable) {
+    download.saver = DownloadSaver.fromSerializable(aSerializable.saver);
+  } else {
+    download.saver = DownloadSaver.fromSerializable("copy");
+  }
+  download.saver.download = download;
+
+  if ("startTime" in aSerializable) {
+    let time = aSerializable.startTime.getTime
+             ? aSerializable.startTime.getTime()
+             : aSerializable.startTime;
+    download.startTime = new Date(time);
+  }
+
+  // If 'errorObj' is present it will take precedence over the 'error' property.
+  // 'error' is a legacy property only containing message, which is insufficient
+  // to represent all of the error information.
+  //
+  // Instead of just replacing 'error' we use a new 'errorObj' so that previous
+  // versions will keep it as an unknown property.
+  if ("errorObj" in aSerializable) {
+    download.error = DownloadError.fromSerializable(aSerializable.errorObj);
+  } else if ("error" in aSerializable) {
+    download.error = aSerializable.error;
+  }
+
+  for (let property of kPlainSerializableDownloadProperties) {
+    if (property in aSerializable) {
+      download[property] = aSerializable[property];
+    }
+  }
+
+  deserializeUnknownProperties(download, aSerializable, property =>
+    kPlainSerializableDownloadProperties.indexOf(property) == -1 &&
+    property != "startTime" &&
+    property != "source" &&
+    property != "target" &&
+    property != "error" &&
+    property != "saver");
+
+  return download;
+};
+
+// DownloadSource
+
+/**
+ * Represents the source of a download, for example a document or an URI.
+ */
+this.DownloadSource = function () {}
+
+this.DownloadSource.prototype = {
+  /**
+   * String containing the URI for the download source.
+   */
+  url: null,
+
+  /**
+   * Indicates whether the download originated from a private window.  This
+   * determines the context of the network request that is made to retrieve the
+   * resource.
+   */
+  isPrivate: false,
+
+  /**
+   * String containing the referrer URI of the download source, or null if no
+   * referrer should be sent or the download source is not HTTP.
+   */
+  referrer: null,
+
+  /**
+   * For downloads handled by the (default) DownloadCopySaver, this function
+   * can adjust the network channel before it is opened, for example to change
+   * the HTTP headers or to upload a stream as POST data.
+   *
+   * @note If this is defined this object will not be serializable, thus the
+   *       Download object will not be persisted across sessions.
+   *
+   * @param aChannel
+   *        The nsIChannel to be adjusted.
+   *
+   * @return {Promise}
+   * @resolves When the channel has been adjusted and can be opened.
+   * @rejects JavaScript exception that will cause the download to fail.
+   */
+   adjustChannel: null,
+
+  /**
+   * Returns a static representation of the current object state.
+   *
+   * @return A JavaScript object that can be serialized to JSON.
+   */
+  toSerializable: function ()
+  {
+    if (this.adjustChannel) {
+      // If the callback was used, we can't reproduce this across sessions.
+      return null;
+    }
+
+    // Simplify the representation if we don't have other details.
+    if (!this.isPrivate && !this.referrer && !this._unknownProperties) {
+      return this.url;
+    }
+
+    let serializable = { url: this.url };
+    if (this.isPrivate) {
+      serializable.isPrivate = true;
+    }
+    if (this.referrer) {
+      serializable.referrer = this.referrer;
+    }
+
+    serializeUnknownProperties(this, serializable);
+    return serializable;
+  },
+};
+
+/**
+ * Creates a new DownloadSource object from its serializable representation.
+ *
+ * @param aSerializable
+ *        Serializable representation of a DownloadSource object.  This may be a
+ *        string containing the URI for the download source, an nsIURI, or an
+ *        object with the following properties:
+ *        {
+ *          url: String containing the URI for the download source.
+ *          isPrivate: Indicates whether the download originated from a private
+ *                     window.  If omitted, the download is public.
+ *          referrer: String containing the referrer URI of the download source.
+ *                    Can be omitted or null if no referrer should be sent or
+ *                    the download source is not HTTP.
+ *          adjustChannel: For downloads handled by (default) DownloadCopySaver,
+ *                         this function can adjust the network channel before
+ *                         it is opened, for example to change the HTTP headers
+ *                         or to upload a stream as POST data.  Optional.
+ *        }
+ *
+ * @return The newly created DownloadSource object.
+ */
+this.DownloadSource.fromSerializable = function (aSerializable) {
+  let source = new DownloadSource();
+  if (isString(aSerializable)) {
+    // Convert String objects to primitive strings at this point.
+    source.url = aSerializable.toString();
+  } else if (aSerializable instanceof Ci.nsIURI) {
+    source.url = aSerializable.spec;
+  } else if (aSerializable instanceof Ci.nsIDOMWindow) {
+    source.url = aSerializable.location.href;
+    source.isPrivate = PrivateBrowsingUtils.isContentWindowPrivate(aSerializable);
+    source.windowRef = Cu.getWeakReference(aSerializable);
+  } else {
+    // Convert String objects to primitive strings at this point.
+    source.url = aSerializable.url.toString();
+    if ("isPrivate" in aSerializable) {
+      source.isPrivate = aSerializable.isPrivate;
+    }
+    if ("referrer" in aSerializable) {
+      source.referrer = aSerializable.referrer;
+    }
+    if ("adjustChannel" in aSerializable) {
+      source.adjustChannel = aSerializable.adjustChannel;
+    }
+
+    deserializeUnknownProperties(source, aSerializable, property =>
+      property != "url" && property != "isPrivate" && property != "referrer");
+  }
+
+  return source;
+};
+
+// DownloadTarget
+
+/**
+ * Represents the target of a download, for example a file in the global
+ * downloads directory, or a file in the system temporary directory.
+ */
+this.DownloadTarget = function () {}
+
+this.DownloadTarget.prototype = {
+  /**
+   * String containing the path of the target file.
+   */
+  path: null,
+
+  /**
+   * String containing the path of the ".part" file containing the data
+   * downloaded so far, or null to disable the use of a ".part" file to keep
+   * partially downloaded data.
+   */
+  partFilePath: null,
+
+  /**
+   * Indicates whether the target file exists.
+   *
+   * This is a dynamic property updated when the download finishes or when the
+   * "refresh" method of the Download object is called. It can be used by the
+   * front-end to reduce I/O compared to checking the target file directly.
+   */
+  exists: false,
+
+  /**
+   * Size in bytes of the target file, or zero if the download has not finished.
+   *
+   * Even if the target file does not exist anymore, this property may still
+   * have a value taken from the download metadata. If the metadata has never
+   * been available in this session and the size cannot be obtained from the
+   * file because it has already been deleted, this property will be zero.
+   *
+   * For single-file downloads, this property will always match the actual file
+   * size on disk, while the totalBytes property of the Download object, when
+   * available, may represent the size of the encoded data instead.
+   *
+   * For downloads involving multiple files, like complete web pages saved to
+   * disk, the meaning of this value is undefined. It currently matches the size
+   * of the main file only rather than the sum of all the written data.
+   *
+   * This is a dynamic property updated when the download finishes or when the
+   * "refresh" method of the Download object is called. It can be used by the
+   * front-end to reduce I/O compared to checking the target file directly.
+   */
+  size: 0,
+
+  /**
+   * Sets the "exists" and "size" properties based on the actual file on disk.
+   *
+   * @return {Promise}
+   * @resolves When the operation has finished successfully.
+   * @rejects JavaScript exception.
+   */
+  refresh: Task.async(function* () {
+    try {
+      this.size = (yield OS.File.stat(this.path)).size;
+      this.exists = true;
+    } catch (ex) {
+      // Report any error not caused by the file not being there. In any case,
+      // the size of the download is not updated and the known value is kept.
+      if (!(ex instanceof OS.File.Error && ex.becauseNoSuchFile)) {
+        Cu.reportError(ex);
+      }
+      this.exists = false;
+    }
+  }),
+
+  /**
+   * Returns a static representation of the current object state.
+   *
+   * @return A JavaScript object that can be serialized to JSON.
+   */
+  toSerializable: function ()
+  {
+    // Simplify the representation if we don't have other details.
+    if (!this.partFilePath && !this._unknownProperties) {
+      return this.path;
+    }
+
+    let serializable = { path: this.path,
+                         partFilePath: this.partFilePath };
+    serializeUnknownProperties(this, serializable);
+    return serializable;
+  },
+};
+
+/**
+ * Creates a new DownloadTarget object from its serializable representation.
+ *
+ * @param aSerializable
+ *        Serializable representation of a DownloadTarget object.  This may be a
+ *        string containing the path of the target file, an nsIFile, or an
+ *        object with the following properties:
+ *        {
+ *          path: String containing the path of the target file.
+ *          partFilePath: optional string containing the part file path.
+ *        }
+ *
+ * @return The newly created DownloadTarget object.
+ */
+this.DownloadTarget.fromSerializable = function (aSerializable) {
+  let target = new DownloadTarget();
+  if (isString(aSerializable)) {
+    // Convert String objects to primitive strings at this point.
+    target.path = aSerializable.toString();
+  } else if (aSerializable instanceof Ci.nsIFile) {
+    // Read the "path" property of nsIFile after checking the object type.
+    target.path = aSerializable.path;
+  } else {
+    // Read the "path" property of the serializable DownloadTarget
+    // representation, converting String objects to primitive strings.
+    target.path = aSerializable.path.toString();
+    if ("partFilePath" in aSerializable) {
+      target.partFilePath = aSerializable.partFilePath;
+    }
+
+    deserializeUnknownProperties(target, aSerializable, property =>
+      property != "path" && property != "partFilePath");
+  }
+  return target;
+};
+
+// DownloadError
+
+/**
+ * Provides detailed information about a download failure.
+ *
+ * @param aProperties
+ *        Object which may contain any of the following properties:
+ *          {
+ *            result: Result error code, defaulting to Cr.NS_ERROR_FAILURE
+ *            message: String error message to be displayed, or null to use the
+ *                     message associated with the result code.
+ *            inferCause: If true, attempts to determine if the cause of the
+ *                        download is a network failure or a local file failure,
+ *                        based on a set of known values of the result code.
+ *                        This is useful when the error is received by a
+ *                        component that handles both aspects of the download.
+ *          }
+ *        The properties object may also contain any of the DownloadError's
+ *        because properties, which will be set accordingly in the error object.
+ */
+this.DownloadError = function (aProperties)
+{
+  const NS_ERROR_MODULE_BASE_OFFSET = 0x45;
+  const NS_ERROR_MODULE_NETWORK = 6;
+  const NS_ERROR_MODULE_FILES = 13;
+
+  // Set the error name used by the Error object prototype first.
+  this.name = "DownloadError";
+  this.result = aProperties.result || Cr.NS_ERROR_FAILURE;
+  if (aProperties.message) {
+    this.message = aProperties.message;
+  } else if (aProperties.becauseBlocked ||
+             aProperties.becauseBlockedByParentalControls ||
+             aProperties.becauseBlockedByReputationCheck ||
+             aProperties.becauseBlockedByRuntimePermissions) {
+    this.message = "Download blocked.";
+  } else {
+    let exception = new Components.Exception("", this.result);
+    this.message = exception.toString();
+  }
+  if (aProperties.inferCause) {
+    let module = ((this.result & 0x7FFF0000) >> 16) -
+                 NS_ERROR_MODULE_BASE_OFFSET;
+    this.becauseSourceFailed = (module == NS_ERROR_MODULE_NETWORK);
+    this.becauseTargetFailed = (module == NS_ERROR_MODULE_FILES);
+  }
+  else {
+    if (aProperties.becauseSourceFailed) {
+      this.becauseSourceFailed = true;
+    }
+    if (aProperties.becauseTargetFailed) {
+      this.becauseTargetFailed = true;
+    }
+  }
+
+  if (aProperties.becauseBlockedByParentalControls) {
+    this.becauseBlocked = true;
+    this.becauseBlockedByParentalControls = true;
+  } else if (aProperties.becauseBlockedByReputationCheck) {
+    this.becauseBlocked = true;
+    this.becauseBlockedByReputationCheck = true;
+    this.reputationCheckVerdict = aProperties.reputationCheckVerdict || "";
+  } else if (aProperties.becauseBlockedByRuntimePermissions) {
+    this.becauseBlocked = true;
+    this.becauseBlockedByRuntimePermissions = true;
+  } else if (aProperties.becauseBlocked) {
+    this.becauseBlocked = true;
+  }
+
+  if (aProperties.innerException) {
+    this.innerException = aProperties.innerException;
+  }
+
+  this.stack = new Error().stack;
+}
+
+/**
+ * These constants are used by the reputationCheckVerdict property and indicate
+ * the detailed reason why a download is blocked.
+ *
+ * @note These values should not be changed because they can be serialized.
+ */
+this.DownloadError.BLOCK_VERDICT_MALWARE = "Malware";
+this.DownloadError.BLOCK_VERDICT_POTENTIALLY_UNWANTED = "PotentiallyUnwanted";
+this.DownloadError.BLOCK_VERDICT_UNCOMMON = "Uncommon";
+
+this.DownloadError.prototype = {
+  __proto__: Error.prototype,
+
+  /**
+   * The result code associated with this error.
+   */
+  result: false,
+
+  /**
+   * Indicates an error occurred while reading from the remote location.
+   */
+  becauseSourceFailed: false,
+
+  /**
+   * Indicates an error occurred while writing to the local target.
+   */
+  becauseTargetFailed: false,
+
+  /**
+   * Indicates the download failed because it was blocked.  If the reason for
+   * blocking is known, the corresponding property will be also set.
+   */
+  becauseBlocked: false,
+
+  /**
+   * Indicates the download was blocked because downloads are globally
+   * disallowed by the Parental Controls or Family Safety features on Windows.
+   */
+  becauseBlockedByParentalControls: false,
+
+  /**
+   * Indicates the download was blocked because it failed the reputation check
+   * and may be malware.
+   */
+  becauseBlockedByReputationCheck: false,
+
+  /**
+   * Indicates the download was blocked because a runtime permission required to
+   * download files was not granted.
+   *
+   * This does not apply to all systems. On Android this flag is set to true if
+   * a needed runtime permission (storage) has not been granted by the user.
+   */
+  becauseBlockedByRuntimePermissions: false,
+
+  /**
+   * If becauseBlockedByReputationCheck is true, indicates the detailed reason
+   * why the download was blocked, according to the "BLOCK_VERDICT_" constants.
+   *
+   * If the download was not blocked or the reason for the block is unknown,
+   * this will be an empty string.
+   */
+  reputationCheckVerdict: "",
+
+  /**
+   * If this DownloadError was caused by an exception this property will
+   * contain the original exception. This will not be serialized when saving
+   * to the store.
+   */
+  innerException: null,
+
+  /**
+   * Returns a static representation of the current object state.
+   *
+   * @return A JavaScript object that can be serialized to JSON.
+   */
+  toSerializable: function ()
+  {
+    let serializable = {
+      result: this.result,
+      message: this.message,
+      becauseSourceFailed: this.becauseSourceFailed,
+      becauseTargetFailed: this.becauseTargetFailed,
+      becauseBlocked: this.becauseBlocked,
+      becauseBlockedByParentalControls: this.becauseBlockedByParentalControls,
+      becauseBlockedByReputationCheck: this.becauseBlockedByReputationCheck,
+      becauseBlockedByRuntimePermissions: this.becauseBlockedByRuntimePermissions,
+      reputationCheckVerdict: this.reputationCheckVerdict,
+    };
+
+    serializeUnknownProperties(this, serializable);
+    return serializable;
+  },
+};
+
+/**
+ * Creates a new DownloadError object from its serializable representation.
+ *
+ * @param aSerializable
+ *        Serializable representation of a DownloadError object.
+ *
+ * @return The newly created DownloadError object.
+ */
+this.DownloadError.fromSerializable = function (aSerializable) {
+  let e = new DownloadError(aSerializable);
+  deserializeUnknownProperties(e, aSerializable, property =>
+    property != "result" &&
+    property != "message" &&
+    property != "becauseSourceFailed" &&
+    property != "becauseTargetFailed" &&
+    property != "becauseBlocked" &&
+    property != "becauseBlockedByParentalControls" &&
+    property != "becauseBlockedByReputationCheck" &&
+    property != "becauseBlockedByRuntimePermissions" &&
+    property != "reputationCheckVerdict");
+
+  return e;
+};
+
+// DownloadSaver
+
+/**
+ * Template for an object that actually transfers the data for the download.
+ */
+this.DownloadSaver = function () {}
+
+this.DownloadSaver.prototype = {
+  /**
+   * Download object for raising notifications and reading properties.
+   *
+   * If the tryToKeepPartialData property of the download object is false, the
+   * saver should never try to keep partially downloaded data if the download
+   * fails.
+   */
+  download: null,
+
+  /**
+   * Executes the download.
+   *
+   * @param aSetProgressBytesFn
+   *        This function may be called by the saver to report progress. It
+   *        takes three arguments: the first is the number of bytes transferred
+   *        until now, the second is the total number of bytes to be
+   *        transferred (or -1 if unknown), the third indicates whether the
+   *        partially downloaded data can be used when restarting the download
+   *        if it fails or is canceled.
+   * @param aSetPropertiesFn
+   *        This function may be called by the saver to report information
+   *        about new download properties discovered by the saver during the
+   *        download process. It takes an object where the keys represents
+   *        the names of the properties to set, and the value represents the
+   *        value to set.
+   *
+   * @return {Promise}
+   * @resolves When the download has finished successfully.
+   * @rejects JavaScript exception if the download failed.
+   */
+  execute: function DS_execute(aSetProgressBytesFn, aSetPropertiesFn)
+  {
+    throw new Error("Not implemented.");
+  },
+
+  /**
+   * Cancels the download.
+   */
+  cancel: function DS_cancel()
+  {
+    throw new Error("Not implemented.");
+  },
+
+  /**
+   * Removes any partial data kept as part of a canceled or failed download.
+   *
+   * This method is never called until the promise returned by "execute" is
+   * either resolved or rejected, and the "execute" method is not called again
+   * until the promise returned by this method is resolved or rejected.
+   *
+   * @return {Promise}
+   * @resolves When the operation has finished successfully.
+   * @rejects JavaScript exception.
+   */
+  removePartialData: function DS_removePartialData()
+  {
+    return Promise.resolve();
+  },
+
+  /**
+   * This can be called by the saver implementation when the download is already
+   * started, to add it to the browsing history.  This method has no effect if
+   * the download is private.
+   */
+  addToHistory: function ()
+  {
+    if (this.download.source.isPrivate) {
+      return;
+    }
+
+    let sourceUri = NetUtil.newURI(this.download.source.url);
+    let referrer = this.download.source.referrer;
+    let referrerUri = referrer ? NetUtil.newURI(referrer) : null;
+    let targetUri = NetUtil.newURI(new FileUtils.File(
+                                       this.download.target.path));
+
+    // The start time is always available when we reach this point.
+    let startPRTime = this.download.startTime.getTime() * 1000;
+
+    try {
+      gDownloadHistory.addDownload(sourceUri, referrerUri, startPRTime,
+                                   targetUri);
+    }
+    catch (ex) {
+      if (!(ex instanceof Components.Exception) ||
+          ex.result != Cr.NS_ERROR_NOT_AVAILABLE) {
+        throw ex;
+      }
+      //
+      // Under normal operation the download history service may not
+      // be available. We don't want all downloads that are public to fail
+      // when this happens so we'll ignore this error and this error only!
+      //
+    }
+  },
+
+  /**
+   * Returns a static representation of the current object state.
+   *
+   * @return A JavaScript object that can be serialized to JSON.
+   */
+  toSerializable: function ()
+  {
+    throw new Error("Not implemented.");
+  },
+
+  /**
+   * Returns the SHA-256 hash of the downloaded file, if it exists.
+   */
+  getSha256Hash: function ()
+  {
+    throw new Error("Not implemented.");
+  },
+
+  getSignatureInfo: function ()
+  {
+    throw new Error("Not implemented.");
+  },
+}; // DownloadSaver
+
+/**
+ * Creates a new DownloadSaver object from its serializable representation.
+ *
+ * @param aSerializable
+ *        Serializable representation of a DownloadSaver object.  If no initial
+ *        state information for the saver object is needed, can be a string
+ *        representing the class of the download operation, for example "copy".
+ *
+ * @return The newly created DownloadSaver object.
+ */
+this.DownloadSaver.fromSerializable = function (aSerializable) {
+  let serializable = isString(aSerializable) ? { type: aSerializable }
+                                             : aSerializable;
+  let saver;
+  switch (serializable.type) {
+    case "copy":
+      saver = DownloadCopySaver.fromSerializable(serializable);
+      break;
+    case "legacy":
+      saver = DownloadLegacySaver.fromSerializable(serializable);
+      break;
+    case "pdf":
+      saver = DownloadPDFSaver.fromSerializable(serializable);
+      break;
+    default:
+      throw new Error("Unrecoginzed download saver type.");
+  }
+  return saver;
+};
+
+// DownloadCopySaver
+
+/**
+ * Saver object that simply copies the entire source file to the target.
+ */
+this.DownloadCopySaver = function () {}
+
+this.DownloadCopySaver.prototype = {
+  __proto__: DownloadSaver.prototype,
+
+  /**
+   * BackgroundFileSaver object currently handling the download.
+   */
+  _backgroundFileSaver: null,
+
+  /**
+   * Indicates whether the "cancel" method has been called.  This is used to
+   * prevent the request from starting in case the operation is canceled before
+   * the BackgroundFileSaver instance has been created.
+   */
+  _canceled: false,
+
+  /**
+   * Save the SHA-256 hash in raw bytes of the downloaded file. This is null
+   * unless BackgroundFileSaver has successfully completed saving the file.
+   */
+  _sha256Hash: null,
+
+  /**
+   * Save the signature info as an nsIArray of nsIX509CertList of nsIX509Cert
+   * if the file is signed. This is empty if the file is unsigned, and null
+   * unless BackgroundFileSaver has successfully completed saving the file.
+   */
+  _signatureInfo: null,
+
+  /**
+   * Save the redirects chain as an nsIArray of nsIPrincipal.
+   */
+  _redirects: null,
+
+  /**
+   * True if the associated download has already been added to browsing history.
+   */
+  alreadyAddedToHistory: false,
+
+  /**
+   * String corresponding to the entityID property of the nsIResumableChannel
+   * used to execute the download, or null if the channel was not resumable or
+   * the saver was instructed not to keep partially downloaded data.
+   */
+  entityID: null,
+
+  /**
+   * Implements "DownloadSaver.execute".
+   */
+  execute: function DCS_execute(aSetProgressBytesFn, aSetPropertiesFn)
+  {
+    let copySaver = this;
+
+    this._canceled = false;
+
+    let download = this.download;
+    let targetPath = download.target.path;
+    let partFilePath = download.target.partFilePath;
+    let keepPartialData = download.tryToKeepPartialData;
+
+    return Task.spawn(function* task_DCS_execute() {
+      // Add the download to history the first time it is started in this
+      // session.  If the download is restarted in a different session, a new
+      // history visit will be added.  We do this just to avoid the complexity
+      // of serializing this state between sessions, since adding a new visit
+      // does not have any noticeable side effect.
+      if (!this.alreadyAddedToHistory) {
+        this.addToHistory();
+        this.alreadyAddedToHistory = true;
+      }
+
+      // To reduce the chance that other downloads reuse the same final target
+      // file name, we should create a placeholder as soon as possible, before
+      // starting the network request.  The placeholder is also required in case
+      // we are using a ".part" file instead of the final target while the
+      // download is in progress.
+      try {
+        // If the file already exists, don't delete its contents yet.
+        let file = yield OS.File.open(targetPath, { write: true });
+        yield file.close();
+      } catch (ex) {
+        if (!(ex instanceof OS.File.Error)) {
+          throw ex;
+        }
+        // Throw a DownloadError indicating that the operation failed because of
+        // the target file.  We cannot translate this into a specific result
+        // code, but we preserve the original message using the toString method.
+        let error = new DownloadError({ message: ex.toString() });
+        error.becauseTargetFailed = true;
+        throw error;
+      }
+
+      try {
+        let deferSaveComplete = Promise.defer();
+
+        if (this._canceled) {
+          // Don't create the BackgroundFileSaver object if we have been
+          // canceled meanwhile.
+          throw new DownloadError({ message: "Saver canceled." });
+        }
+
+        // Create the object that will save the file in a background thread.
+        let backgroundFileSaver = new BackgroundFileSaverStreamListener();
+        try {
+          // When the operation completes, reflect the status in the promise
+          // returned by this download execution function.
+          backgroundFileSaver.observer = {
+            onTargetChange: function () { },
+            onSaveComplete: (aSaver, aStatus) => {
+              // Send notifications now that we can restart if needed.
+              if (Components.isSuccessCode(aStatus)) {
+                // Save the hash before freeing backgroundFileSaver.
+                this._sha256Hash = aSaver.sha256Hash;
+                this._signatureInfo = aSaver.signatureInfo;
+                this._redirects = aSaver.redirects;
+                deferSaveComplete.resolve();
+              } else {
+                // Infer the origin of the error from the failure code, because
+                // BackgroundFileSaver does not provide more specific data.
+                let properties = { result: aStatus, inferCause: true };
+                deferSaveComplete.reject(new DownloadError(properties));
+              }
+              // Free the reference cycle, to release resources earlier.
+              backgroundFileSaver.observer = null;
+              this._backgroundFileSaver = null;
+            },
+          };
+
+          // Create a channel from the source, and listen to progress
+          // notifications.
+          let channel = NetUtil.newChannel({
+            uri: download.source.url,
+            loadUsingSystemPrincipal: true,
+          });
+          if (channel instanceof Ci.nsIPrivateBrowsingChannel) {
+            channel.setPrivate(download.source.isPrivate);
+          }
+          if (channel instanceof Ci.nsIHttpChannel &&
+              download.source.referrer) {
+            channel.referrer = NetUtil.newURI(download.source.referrer);
+          }
+
+          // If we have data that we can use to resume the download from where
+          // it stopped, try to use it.
+          let resumeAttempted = false;
+          let resumeFromBytes = 0;
+          if (channel instanceof Ci.nsIResumableChannel && this.entityID &&
+              partFilePath && keepPartialData) {
+            try {
+              let stat = yield OS.File.stat(partFilePath);
+              channel.resumeAt(stat.size, this.entityID);
+              resumeAttempted = true;
+              resumeFromBytes = stat.size;
+            } catch (ex) {
+              if (!(ex instanceof OS.File.Error) || !ex.becauseNoSuchFile) {
+                throw ex;
+              }
+            }
+          }
+
+          channel.notificationCallbacks = {
+            QueryInterface: XPCOMUtils.generateQI([Ci.nsIInterfaceRequestor]),
+            getInterface: XPCOMUtils.generateQI([Ci.nsIProgressEventSink]),
+            onProgress: function DCSE_onProgress(aRequest, aContext, aProgress,
+                                                 aProgressMax)
+            {
+              let currentBytes = resumeFromBytes + aProgress;
+              let totalBytes = aProgressMax == -1 ? -1 : (resumeFromBytes +
+                                                          aProgressMax);
+              aSetProgressBytesFn(currentBytes, totalBytes, aProgress > 0 &&
+                                  partFilePath && keepPartialData);
+            },
+            onStatus: function () { },
+          };
+
+          // If the callback was set, handle it now before opening the channel.
+          if (download.source.adjustChannel) {
+            yield download.source.adjustChannel(channel);
+          }
+
+          // Open the channel, directing output to the background file saver.
+          backgroundFileSaver.QueryInterface(Ci.nsIStreamListener);
+          channel.asyncOpen2({
+            onStartRequest: function (aRequest, aContext) {
+              backgroundFileSaver.onStartRequest(aRequest, aContext);
+
+              // Check if the request's response has been blocked by Windows
+              // Parental Controls with an HTTP 450 error code.
+              if (aRequest instanceof Ci.nsIHttpChannel &&
+                  aRequest.responseStatus == 450) {
+                // Set a flag that can be retrieved later when handling the
+                // cancellation so that the proper error can be thrown.
+                this.download._blockedByParentalControls = true;
+                aRequest.cancel(Cr.NS_BINDING_ABORTED);
+                return;
+              }
+
+              aSetPropertiesFn({ contentType: channel.contentType });
+
+              // Ensure we report the value of "Content-Length", if available,
+              // even if the download doesn't generate any progress events
+              // later.
+              if (channel.contentLength >= 0) {
+                aSetProgressBytesFn(0, channel.contentLength);
+              }
+
+              // If the URL we are downloading from includes a file extension
+              // that matches the "Content-Encoding" header, for example ".gz"
+              // with a "gzip" encoding, we should save the file in its encoded
+              // form.  In all other cases, we decode the body while saving.
+              if (channel instanceof Ci.nsIEncodedChannel &&
+                  channel.contentEncodings) {
+                let uri = channel.URI;
+                if (uri instanceof Ci.nsIURL && uri.fileExtension) {
+                  // Only the first, outermost encoding is considered.
+                  let encoding = channel.contentEncodings.getNext();
+                  if (encoding) {
+                    channel.applyConversion =
+                      gExternalHelperAppService.applyDecodingForExtension(
+                                                uri.fileExtension, encoding);
+                  }
+                }
+              }
+
+              if (keepPartialData) {
+                // If the source is not resumable, don't keep partial data even
+                // if we were asked to try and do it.
+                if (aRequest instanceof Ci.nsIResumableChannel) {
+                  try {
+                    // If reading the ID succeeds, the source is resumable.
+                    this.entityID = aRequest.entityID;
+                  } catch (ex) {
+                    if (!(ex instanceof Components.Exception) ||
+                        ex.result != Cr.NS_ERROR_NOT_RESUMABLE) {
+                      throw ex;
+                    }
+                    keepPartialData = false;
+                  }
+                } else {
+                  keepPartialData = false;
+                }
+              }
+
+              // Enable hashing and signature verification before setting the
+              // target.
+              backgroundFileSaver.enableSha256();
+              backgroundFileSaver.enableSignatureInfo();
+              if (partFilePath) {
+                // If we actually resumed a request, append to the partial data.
+                if (resumeAttempted) {
+                  // TODO: Handle Cr.NS_ERROR_ENTITY_CHANGED
+                  backgroundFileSaver.enableAppend();
+                }
+
+                // Use a part file, determining if we should keep it on failure.
+                backgroundFileSaver.setTarget(new FileUtils.File(partFilePath),
+                                              keepPartialData);
+              } else {
+                // Set the final target file, and delete it on failure.
+                backgroundFileSaver.setTarget(new FileUtils.File(targetPath),
+                                              false);
+              }
+            }.bind(copySaver),
+
+            onStopRequest: function (aRequest, aContext, aStatusCode) {
+              try {
+                backgroundFileSaver.onStopRequest(aRequest, aContext,
+                                                  aStatusCode);
+              } finally {
+                // If the data transfer completed successfully, indicate to the
+                // background file saver that the operation can finish.  If the
+                // data transfer failed, the saver has been already stopped.
+                if (Components.isSuccessCode(aStatusCode)) {
+                  backgroundFileSaver.finish(Cr.NS_OK);
+                }
+              }
+            }.bind(copySaver),
+
+            onDataAvailable: function (aRequest, aContext, aInputStream,
+                                       aOffset, aCount) {
+              backgroundFileSaver.onDataAvailable(aRequest, aContext,
+                                                  aInputStream, aOffset,
+                                                  aCount);
+            }.bind(copySaver),
+          });
+
+          // We should check if we have been canceled in the meantime, after
+          // all the previous asynchronous operations have been executed and
+          // just before we set the _backgroundFileSaver property.
+          if (this._canceled) {
+            throw new DownloadError({ message: "Saver canceled." });
+          }
+
+          // If the operation succeeded, store the object to allow cancellation.
+          this._backgroundFileSaver = backgroundFileSaver;
+        } catch (ex) {
+          // In case an error occurs while setting up the chain of objects for
+          // the download, ensure that we release the resources of the saver.
+          backgroundFileSaver.finish(Cr.NS_ERROR_FAILURE);
+          // Since we're not going to handle deferSaveComplete.promise below,
+          // we need to make sure that the rejection is handled.
+          deferSaveComplete.promise.catch(() => {});
+          throw ex;
+        }
+
+        // We will wait on this promise in case no error occurred while setting
+        // up the chain of objects for the download.
+        yield deferSaveComplete.promise;
+
+        yield this._checkReputationAndMove(aSetPropertiesFn);
+      } catch (ex) {
+        // Ensure we always remove the placeholder for the final target file on
+        // failure, independently of which code path failed.  In some cases, the
+        // background file saver may have already removed the file.
+        try {
+          yield OS.File.remove(targetPath);
+        } catch (e2) {
+          // If we failed during the operation, we report the error but use the
+          // original one as the failure reason of the download.  Note that on
+          // Windows we may get an access denied error instead of a no such file
+          // error if the file existed before, and was recently deleted.
+          if (!(e2 instanceof OS.File.Error &&
+                (e2.becauseNoSuchFile || e2.becauseAccessDenied))) {
+            Cu.reportError(e2);
+          }
+        }
+        throw ex;
+      }
+    }.bind(this));
+  },
+
+  /**
+   * Perform the reputation check and cleanup the downloaded data if required.
+   * If the download passes the reputation check and is using a part file we
+   * will move it to the target path since reputation checking is the final
+   * step in the saver.
+   *
+   * @param aSetPropertiesFn
+   *        Function provided to the "execute" method.
+   *
+   * @return {Promise}
+   * @resolves When the reputation check and cleanup is complete.
+   * @rejects DownloadError if the download should be blocked.
+   */
+  _checkReputationAndMove: Task.async(function* (aSetPropertiesFn) {
+    let download = this.download;
+    let targetPath = this.download.target.path;
+    let partFilePath = this.download.target.partFilePath;
+
+    let { shouldBlock, verdict } =
+        yield DownloadIntegration.shouldBlockForReputationCheck(download);
+    if (shouldBlock) {
+      let newProperties = { progress: 100, hasPartialData: false };
+
+      // We will remove the potentially dangerous file if instructed by
+      // DownloadIntegration. We will always remove the file when the
+      // download did not use a partial file path, meaning it
+      // currently has its final filename.
+      if (!DownloadIntegration.shouldKeepBlockedData() || !partFilePath) {
+        try {
+          yield OS.File.remove(partFilePath || targetPath);
+        } catch (ex) {
+          Cu.reportError(ex);
+        }
+      } else {
+        newProperties.hasBlockedData = true;
+      }
+
+      aSetPropertiesFn(newProperties);
+
+      throw new DownloadError({
+        becauseBlockedByReputationCheck: true,
+        reputationCheckVerdict: verdict,
+      });
+    }
+
+    if (partFilePath) {
+      yield OS.File.move(partFilePath, targetPath);
+    }
+  }),
+
+  /**
+   * Implements "DownloadSaver.cancel".
+   */
+  cancel: function DCS_cancel()
+  {
+    this._canceled = true;
+    if (this._backgroundFileSaver) {
+      this._backgroundFileSaver.finish(Cr.NS_ERROR_FAILURE);
+      this._backgroundFileSaver = null;
+    }
+  },
+
+  /**
+   * Implements "DownloadSaver.removePartialData".
+   */
+  removePartialData: function ()
+  {
+    return Task.spawn(function* task_DCS_removePartialData() {
+      if (this.download.target.partFilePath) {
+        try {
+          yield OS.File.remove(this.download.target.partFilePath);
+        } catch (ex) {
+          if (!(ex instanceof OS.File.Error) || !ex.becauseNoSuchFile) {
+            throw ex;
+          }
+        }
+      }
+    }.bind(this));
+  },
+
+  /**
+   * Implements "DownloadSaver.toSerializable".
+   */
+  toSerializable: function ()
+  {
+    // Simplify the representation if we don't have other details.
+    if (!this.entityID && !this._unknownProperties) {
+      return "copy";
+    }
+
+    let serializable = { type: "copy",
+                         entityID: this.entityID };
+    serializeUnknownProperties(this, serializable);
+    return serializable;
+  },
+
+  /**
+   * Implements "DownloadSaver.getSha256Hash"
+   */
+  getSha256Hash: function ()
+  {
+    return this._sha256Hash;
+  },
+
+  /*
+   * Implements DownloadSaver.getSignatureInfo.
+   */
+  getSignatureInfo: function ()
+  {
+    return this._signatureInfo;
+  },
+
+  /*
+   * Implements DownloadSaver.getRedirects.
+   */
+  getRedirects: function ()
+  {
+    return this._redirects;
+  }
+};
+
+/**
+ * Creates a new DownloadCopySaver object, with its initial state derived from
+ * its serializable representation.
+ *
+ * @param aSerializable
+ *        Serializable representation of a DownloadCopySaver object.
+ *
+ * @return The newly created DownloadCopySaver object.
+ */
+this.DownloadCopySaver.fromSerializable = function (aSerializable) {
+  let saver = new DownloadCopySaver();
+  if ("entityID" in aSerializable) {
+    saver.entityID = aSerializable.entityID;
+  }
+
+  deserializeUnknownProperties(saver, aSerializable, property =>
+    property != "entityID" && property != "type");
+
+  return saver;
+};
+
+// DownloadLegacySaver
+
+/**
+ * Saver object that integrates with the legacy nsITransfer interface.
+ *
+ * For more background on the process, see the DownloadLegacyTransfer object.
+ */
+this.DownloadLegacySaver = function ()
+{
+  this.deferExecuted = Promise.defer();
+  this.deferCanceled = Promise.defer();
+}
+
+this.DownloadLegacySaver.prototype = {
+  __proto__: DownloadSaver.prototype,
+
+  /**
+   * Save the SHA-256 hash in raw bytes of the downloaded file. This may be
+   * null when nsExternalHelperAppService (and thus BackgroundFileSaver) is not
+   * invoked.
+   */
+  _sha256Hash: null,
+
+  /**
+   * Save the signature info as an nsIArray of nsIX509CertList of nsIX509Cert
+   * if the file is signed. This is empty if the file is unsigned, and null
+   * unless BackgroundFileSaver has successfully completed saving the file.
+   */
+  _signatureInfo: null,
+
+  /**
+   * Save the redirect chain as an nsIArray of nsIPrincipal.
+   */
+  _redirects: null,
+
+  /**
+   * nsIRequest object associated to the status and progress updates we
+   * received.  This object is null before we receive the first status and
+   * progress update, and is also reset to null when the download is stopped.
+   */
+  request: null,
+
+  /**
+   * This deferred object contains a promise that is resolved as soon as this
+   * download finishes successfully, and is rejected in case the download is
+   * canceled or receives a failure notification through nsITransfer.
+   */
+  deferExecuted: null,
+
+  /**
+   * This deferred object contains a promise that is resolved if the download
+   * receives a cancellation request through the "cancel" method, and is never
+   * rejected.  The nsITransfer implementation will register a handler that
+   * actually causes the download cancellation.
+   */
+  deferCanceled: null,
+
+  /**
+   * This is populated with the value of the aSetProgressBytesFn argument of the
+   * "execute" method, and is null before the method is called.
+   */
+  setProgressBytesFn: null,
+
+  /**
+   * Called by the nsITransfer implementation while the download progresses.
+   *
+   * @param aCurrentBytes
+   *        Number of bytes transferred until now.
+   * @param aTotalBytes
+   *        Total number of bytes to be transferred, or -1 if unknown.
+   */
+  onProgressBytes: function DLS_onProgressBytes(aCurrentBytes, aTotalBytes)
+  {
+    this.progressWasNotified = true;
+
+    // Ignore progress notifications until we are ready to process them.
+    if (!this.setProgressBytesFn) {
+      // Keep the data from the last progress notification that was received.
+      this.currentBytes = aCurrentBytes;
+      this.totalBytes = aTotalBytes;
+      return;
+    }
+
+    let hasPartFile = !!this.download.target.partFilePath;
+
+    this.setProgressBytesFn(aCurrentBytes, aTotalBytes,
+                            aCurrentBytes > 0 && hasPartFile);
+  },
+
+  /**
+   * Whether the onProgressBytes function has been called at least once.
+   */
+  progressWasNotified: false,
+
+  /**
+   * Called by the nsITransfer implementation when the request has started.
+   *
+   * @param aRequest
+   *        nsIRequest associated to the status update.
+   * @param aAlreadyAddedToHistory
+   *        Indicates that the nsIExternalHelperAppService component already
+   *        added the download to the browsing history, unless it was started
+   *        from a private browsing window.  When this parameter is false, the
+   *        download is added to the browsing history here.  Private downloads
+   *        are never added to history even if this parameter is false.
+   */
+  onTransferStarted: function (aRequest, aAlreadyAddedToHistory)
+  {
+    // Store the entity ID to use for resuming if required.
+    if (this.download.tryToKeepPartialData &&
+        aRequest instanceof Ci.nsIResumableChannel) {
+      try {
+        // If reading the ID succeeds, the source is resumable.
+        this.entityID = aRequest.entityID;
+      } catch (ex) {
+        if (!(ex instanceof Components.Exception) ||
+            ex.result != Cr.NS_ERROR_NOT_RESUMABLE) {
+          throw ex;
+        }
+      }
+    }
+
+    // For legacy downloads, we must update the referrer at this time.
+    if (aRequest instanceof Ci.nsIHttpChannel && aRequest.referrer) {
+      this.download.source.referrer = aRequest.referrer.spec;
+    }
+
+    if (!aAlreadyAddedToHistory) {
+      this.addToHistory();
+    }
+  },
+
+  /**
+   * Called by the nsITransfer implementation when the request has finished.
+   *
+   * @param aRequest
+   *        nsIRequest associated to the status update.
+   * @param aStatus
+   *        Status code received by the nsITransfer implementation.
+   */
+  onTransferFinished: function DLS_onTransferFinished(aRequest, aStatus)
+  {
+    // Store a reference to the request, used when handling completion.
+    this.request = aRequest;
+
+    if (Components.isSuccessCode(aStatus)) {
+      this.deferExecuted.resolve();
+    } else {
+      // Infer the origin of the error from the failure code, because more
+      // specific data is not available through the nsITransfer implementation.
+      let properties = { result: aStatus, inferCause: true };
+      this.deferExecuted.reject(new DownloadError(properties));
+    }
+  },
+
+  /**
+   * When the first execution of the download finished, it can be restarted by
+   * using a DownloadCopySaver object instead of the original legacy component
+   * that executed the download.
+   */
+  firstExecutionFinished: false,
+
+  /**
+   * In case the download is restarted after the first execution finished, this
+   * property contains a reference to the DownloadCopySaver that is executing
+   * the new download attempt.
+   */
+  copySaver: null,
+
+  /**
+   * String corresponding to the entityID property of the nsIResumableChannel
+   * used to execute the download, or null if the channel was not resumable or
+   * the saver was instructed not to keep partially downloaded data.
+   */
+  entityID: null,
+
+  /**
+   * Implements "DownloadSaver.execute".
+   */
+  execute: function DLS_execute(aSetProgressBytesFn, aSetPropertiesFn)
+  {
+    // Check if this is not the first execution of the download.  The Download
+    // object guarantees that this function is not re-entered during execution.
+    if (this.firstExecutionFinished) {
+      if (!this.copySaver) {
+        this.copySaver = new DownloadCopySaver();
+        this.copySaver.download = this.download;
+        this.copySaver.entityID = this.entityID;
+        this.copySaver.alreadyAddedToHistory = true;
+      }
+      return this.copySaver.execute.apply(this.copySaver, arguments);
+    }
+
+    this.setProgressBytesFn = aSetProgressBytesFn;
+    if (this.progressWasNotified) {
+      this.onProgressBytes(this.currentBytes, this.totalBytes);
+    }
+
+    return Task.spawn(function* task_DLS_execute() {
+      try {
+        // Wait for the component that executes the download to finish.
+        yield this.deferExecuted.promise;
+
+        // At this point, the "request" property has been populated.  Ensure we
+        // report the value of "Content-Length", if available, even if the
+        // download didn't generate any progress events.
+        if (!this.progressWasNotified &&
+            this.request instanceof Ci.nsIChannel &&
+            this.request.contentLength >= 0) {
+          aSetProgressBytesFn(0, this.request.contentLength);
+        }
+
+        // If the component executing the download provides the path of a
+        // ".part" file, it means that it expects the listener to move the file
+        // to its final target path when the download succeeds.  In this case,
+        // an empty ".part" file is created even if no data was received from
+        // the source.
+        //
+        // When no ".part" file path is provided the download implementation may
+        // not have created the target file (if no data was received from the
+        // source).  In this case, ensure that an empty file is created as
+        // expected.
+        if (!this.download.target.partFilePath) {
+          try {
+            // This atomic operation is more efficient than an existence check.
+            let file = yield OS.File.open(this.download.target.path,
+                                          { create: true });
+            yield file.close();
+          } catch (ex) {
+            if (!(ex instanceof OS.File.Error) || !ex.becauseExists) {
+              throw ex;
+            }
+          }
+        }
+
+        yield this._checkReputationAndMove(aSetPropertiesFn);
+
+      } catch (ex) {
+        // Ensure we always remove the final target file on failure,
+        // independently of which code path failed.  In some cases, the
+        // component executing the download may have already removed the file.
+        try {
+          yield OS.File.remove(this.download.target.path);
+        } catch (e2) {
+          // If we failed during the operation, we report the error but use the
+          // original one as the failure reason of the download.  Note that on
+          // Windows we may get an access denied error instead of a no such file
+          // error if the file existed before, and was recently deleted.
+          if (!(e2 instanceof OS.File.Error &&
+                (e2.becauseNoSuchFile || e2.becauseAccessDenied))) {
+            Cu.reportError(e2);
+          }
+        }
+        // In case the operation failed, ensure we stop downloading data.  Since
+        // we never re-enter this function, deferCanceled is always available.
+        this.deferCanceled.resolve();
+        throw ex;
+      } finally {
+        // We don't need the reference to the request anymore.  We must also set
+        // deferCanceled to null in order to free any indirect references it
+        // may hold to the request.
+        this.request = null;
+        this.deferCanceled = null;
+        // Allow the download to restart through a DownloadCopySaver.
+        this.firstExecutionFinished = true;
+      }
+    }.bind(this));
+  },
+
+  _checkReputationAndMove: function () {
+    return DownloadCopySaver.prototype._checkReputationAndMove
+                                      .apply(this, arguments);
+  },
+
+  /**
+   * Implements "DownloadSaver.cancel".
+   */
+  cancel: function DLS_cancel()
+  {
+    // We may be using a DownloadCopySaver to handle resuming.
+    if (this.copySaver) {
+      return this.copySaver.cancel.apply(this.copySaver, arguments);
+    }
+
+    // If the download hasn't stopped already, resolve deferCanceled so that the
+    // operation is canceled as soon as a cancellation handler is registered.
+    // Note that the handler might not have been registered yet.
+    if (this.deferCanceled) {
+      this.deferCanceled.resolve();
+    }
+  },
+
+  /**
+   * Implements "DownloadSaver.removePartialData".
+   */
+  removePartialData: function ()
+  {
+    // DownloadCopySaver and DownloadLeagcySaver use the same logic for removing
+    // partially downloaded data, though this implementation isn't shared by
+    // other saver types, thus it isn't found on their shared prototype.
+    return DownloadCopySaver.prototype.removePartialData.call(this);
+  },
+
+  /**
+   * Implements "DownloadSaver.toSerializable".
+   */
+  toSerializable: function ()
+  {
+    // This object depends on legacy components that are created externally,
+    // thus it cannot be rebuilt during deserialization.  To support resuming
+    // across different browser sessions, this object is transformed into a
+    // DownloadCopySaver for the purpose of serialization.
+    return DownloadCopySaver.prototype.toSerializable.call(this);
+  },
+
+  /**
+   * Implements "DownloadSaver.getSha256Hash".
+   */
+  getSha256Hash: function ()
+  {
+    if (this.copySaver) {
+      return this.copySaver.getSha256Hash();
+    }
+    return this._sha256Hash;
+  },
+
+  /**
+   * Called by the nsITransfer implementation when the hash is available.
+   */
+  setSha256Hash: function (hash)
+  {
+    this._sha256Hash = hash;
+  },
+
+  /**
+   * Implements "DownloadSaver.getSignatureInfo".
+   */
+  getSignatureInfo: function ()
+  {
+    if (this.copySaver) {
+      return this.copySaver.getSignatureInfo();
+    }
+    return this._signatureInfo;
+  },
+
+  /**
+   * Called by the nsITransfer implementation when the hash is available.
+   */
+  setSignatureInfo: function (signatureInfo)
+  {
+    this._signatureInfo = signatureInfo;
+  },
+
+  /**
+   * Implements "DownloadSaver.getRedirects".
+   */
+  getRedirects: function ()
+  {
+    if (this.copySaver) {
+      return this.copySaver.getRedirects();
+    }
+    return this._redirects;
+  },
+
+  /**
+   * Called by the nsITransfer implementation when the redirect chain is
+   * available.
+   */
+  setRedirects: function (redirects)
+  {
+    this._redirects = redirects;
+  },
+};
+
+/**
+ * Returns a new DownloadLegacySaver object.  This saver type has a
+ * deserializable form only when creating a new object in memory, because it
+ * cannot be serialized to disk.
+ */
+this.DownloadLegacySaver.fromSerializable = function () {
+  return new DownloadLegacySaver();
+};
+
+// DownloadPDFSaver
+
+/**
+ * This DownloadSaver type creates a PDF file from the current document in a
+ * given window, specified using the windowRef property of the DownloadSource
+ * object associated with the download.
+ *
+ * In order to prevent the download from saving a different document than the one
+ * originally loaded in the window, any attempt to restart the download will fail.
+ *
+ * Since this DownloadSaver type requires a live document as a source, it cannot
+ * be persisted across sessions, unless the download already succeeded.
+ */
+this.DownloadPDFSaver = function () {
+}
+
+this.DownloadPDFSaver.prototype = {
+  __proto__: DownloadSaver.prototype,
+
+  /**
+   * An nsIWebBrowserPrint instance for printing this page.
+   * This is null when saving has not started or has completed,
+   * or while the operation is being canceled.
+   */
+  _webBrowserPrint: null,
+
+  /**
+   * Implements "DownloadSaver.execute".
+   */
+  execute: function (aSetProgressBytesFn, aSetPropertiesFn)
+  {
+    return Task.spawn(function* task_DCS_execute() {
+      if (!this.download.source.windowRef) {
+        throw new DownloadError({
+          message: "PDF saver must be passed an open window, and cannot be restarted.",
+          becauseSourceFailed: true,
+        });
+      }
+
+      let win = this.download.source.windowRef.get();
+
+      // Set windowRef to null to avoid re-trying.
+      this.download.source.windowRef = null;
+
+      if (!win) {
+        throw new DownloadError({
+          message: "PDF saver can't save a window that has been closed.",
+          becauseSourceFailed: true,
+        });
+      }
+
+      this.addToHistory();
+
+      let targetPath = this.download.target.path;
+
+      // An empty target file must exist for the PDF printer to work correctly.
+      let file = yield OS.File.open(targetPath, { truncate: true });
+      yield file.close();
+
+      let printSettings = gPrintSettingsService.newPrintSettings;
+
+      printSettings.printToFile = true;
+      printSettings.outputFormat = Ci.nsIPrintSettings.kOutputFormatPDF;
+      printSettings.toFileName = targetPath;
+
+      printSettings.printSilent = true;
+      printSettings.showPrintProgress = false;
+
+      printSettings.printBGImages = true;
+      printSettings.printBGColors = true;
+      printSettings.printFrameType = Ci.nsIPrintSettings.kFramesAsIs;
+      printSettings.headerStrCenter = "";
+      printSettings.headerStrLeft = "";
+      printSettings.headerStrRight = "";
+      printSettings.footerStrCenter = "";
+      printSettings.footerStrLeft = "";
+      printSettings.footerStrRight = "";
+
+      this._webBrowserPrint = win.QueryInterface(Ci.nsIInterfaceRequestor)
+                                 .getInterface(Ci.nsIWebBrowserPrint);
+
+      try {
+        yield new Promise((resolve, reject) => {
+          this._webBrowserPrint.print(printSettings, {
+            onStateChange: function (webProgress, request, stateFlags, status) {
+              if (stateFlags & Ci.nsIWebProgressListener.STATE_STOP) {
+                if (!Components.isSuccessCode(status)) {
+                  reject(new DownloadError({ result: status,
+                                             inferCause: true }));
+                } else {
+                  resolve();
+                }
+              }
+            },
+            onProgressChange: function (webProgress, request, curSelfProgress,
+                                        maxSelfProgress, curTotalProgress,
+                                        maxTotalProgress) {
+              aSetProgressBytesFn(curTotalProgress, maxTotalProgress, false);
+            },
+            onLocationChange: function () {},
+            onStatusChange: function () {},
+            onSecurityChange: function () {},
+          });
+        });
+      } finally {
+        // Remove the print object to avoid leaks
+        this._webBrowserPrint = null;
+      }
+
+      let fileInfo = yield OS.File.stat(targetPath);
+      aSetProgressBytesFn(fileInfo.size, fileInfo.size, false);
+    }.bind(this));
+  },
+
+  /**
+   * Implements "DownloadSaver.cancel".
+   */
+  cancel: function DCS_cancel()
+  {
+    if (this._webBrowserPrint) {
+      this._webBrowserPrint.cancel();
+      this._webBrowserPrint = null;
+    }
+  },
+
+  /**
+   * Implements "DownloadSaver.toSerializable".
+   */
+  toSerializable: function ()
+  {
+    if (this.download.succeeded) {
+      return DownloadCopySaver.prototype.toSerializable.call(this);
+    }
+
+    // This object needs a window to recreate itself. If it didn't succeded
+    // it will not be possible to restart. Returning null here will
+    // prevent us from serializing it at all.
+    return null;
+  },
+};
+
+/**
+ * Creates a new DownloadPDFSaver object, with its initial state derived from
+ * its serializable representation.
+ *
+ * @param aSerializable
+ *        Serializable representation of a DownloadPDFSaver object.
+ *
+ * @return The newly created DownloadPDFSaver object.
+ */
+this.DownloadPDFSaver.fromSerializable = function (aSerializable) {
+  return new DownloadPDFSaver();
+};
diff --git a/toolkit/components/jsdownloads/src/DownloadImport.jsm b/toolkit/components/jsdownloads/src/DownloadImport.jsm
new file mode 100644
index 000000000..5fb7fd0c7
--- /dev/null
+++ b/toolkit/components/jsdownloads/src/DownloadImport.jsm
@@ -0,0 +1,193 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* 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 = [
+  "DownloadImport",
+];
+
+// Globals
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+const Cr = Components.results;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "Downloads",
+                                  "resource://gre/modules/Downloads.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "OS",
+                                  "resource://gre/modules/osfile.jsm")
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+                                  "resource://gre/modules/Task.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Sqlite",
+                                  "resource://gre/modules/Sqlite.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
+                                  "resource://gre/modules/NetUtil.jsm");
+
+/**
+ * These values come from the previous interface
+ * nsIDownloadManager, which has now been deprecated.
+ * These are the only types of download states that
+ * we will import.
+ */
+const DOWNLOAD_NOTSTARTED = -1;
+const DOWNLOAD_DOWNLOADING = 0;
+const DOWNLOAD_PAUSED = 4;
+const DOWNLOAD_QUEUED = 5;
+
+// DownloadImport
+
+/**
+ * Provides an object that has a method to import downloads
+ * from the previous SQLite storage format.
+ *
+ * @param aList   A DownloadList where each successfully
+ *                imported download will be added.
+ * @param aPath   The path to the database file.
+ */
+this.DownloadImport = function (aList, aPath)
+{
+  this.list = aList;
+  this.path = aPath;
+}
+
+this.DownloadImport.prototype = {
+  /**
+   * Imports unfinished downloads from the previous SQLite storage
+   * format (supporting schemas 7 and up), to the new Download object
+   * format. Each imported download will be added to the DownloadList
+   *
+   * @return {Promise}
+   * @resolves When the operation has completed (i.e., every download
+   *           from the previous database has been read and added to
+   *           the DownloadList)
+   */
+  import: function () {
+    return Task.spawn(function* task_DI_import() {
+      let connection = yield Sqlite.openConnection({ path: this.path });
+
+      try {
+        let schemaVersion = yield connection.getSchemaVersion();
+        // We don't support schemas older than version 7 (from 2007)
+        // - Version 7 added the columns mimeType, preferredApplication
+        //   and preferredAction in 2007
+        // - Version 8 added the column autoResume in 2007
+        //   (if we encounter version 7 we will treat autoResume = false)
+        // - Version 9 is the last known version, which added a unique
+        //   GUID text column that is not used here
+        if (schemaVersion < 7) {
+          throw new Error("Unable to import in-progress downloads because "
+                          + "the existing profile is too old.");
+        }
+
+        let rows = yield connection.execute("SELECT * FROM moz_downloads");
+
+        for (let row of rows) {
+          try {
+            // Get the DB row data
+            let source = row.getResultByName("source");
+            let target = row.getResultByName("target");
+            let tempPath = row.getResultByName("tempPath");
+            let startTime = row.getResultByName("startTime");
+            let state = row.getResultByName("state");
+            let referrer = row.getResultByName("referrer");
+            let maxBytes = row.getResultByName("maxBytes");
+            let mimeType = row.getResultByName("mimeType");
+            let preferredApplication = row.getResultByName("preferredApplication");
+            let preferredAction = row.getResultByName("preferredAction");
+            let entityID = row.getResultByName("entityID");
+
+            let autoResume = false;
+            try {
+              autoResume = (row.getResultByName("autoResume") == 1);
+            } catch (ex) {
+              // autoResume wasn't present in schema version 7
+            }
+
+            if (!source) {
+              throw new Error("Attempted to import a row with an empty " +
+                              "source column.");
+            }
+
+            let resumeDownload = false;
+
+            switch (state) {
+              case DOWNLOAD_NOTSTARTED:
+              case DOWNLOAD_QUEUED:
+              case DOWNLOAD_DOWNLOADING:
+                resumeDownload = true;
+                break;
+
+              case DOWNLOAD_PAUSED:
+                resumeDownload = autoResume;
+                break;
+
+              default:
+                // We won't import downloads in other states
+                continue;
+            }
+
+            // Transform the data
+            let targetPath = NetUtil.newURI(target)
+                                    .QueryInterface(Ci.nsIFileURL).file.path;
+
+            let launchWhenSucceeded = (preferredAction != Ci.nsIMIMEInfo.saveToDisk);
+
+            let downloadOptions = {
+              source: {
+                url: source,
+                referrer: referrer
+              },
+              target: {
+                path: targetPath,
+                partFilePath: tempPath,
+              },
+              saver: {
+                type: "copy",
+                entityID: entityID
+              },
+              startTime: new Date(startTime / 1000),
+              totalBytes: maxBytes,
+              hasPartialData: !!tempPath,
+              tryToKeepPartialData: true,
+              launchWhenSucceeded: launchWhenSucceeded,
+              contentType: mimeType,
+              launcherPath: preferredApplication
+            };
+
+            // Paused downloads that should not be auto-resumed are considered
+            // in a "canceled" state.
+            if (!resumeDownload) {
+              downloadOptions.canceled = true;
+            }
+
+            let download = yield Downloads.createDownload(downloadOptions);
+
+            yield this.list.add(download);
+
+            if (resumeDownload) {
+              download.start().catch(() => {});
+            } else {
+              yield download.refresh();
+            }
+
+          } catch (ex) {
+            Cu.reportError("Error importing download: " + ex);
+          }
+        }
+
+      } catch (ex) {
+        Cu.reportError(ex);
+      } finally {
+        yield connection.close();
+      }
+    }.bind(this));
+  }
+}
+
diff --git a/toolkit/components/jsdownloads/src/DownloadIntegration.jsm b/toolkit/components/jsdownloads/src/DownloadIntegration.jsm
new file mode 100644
index 000000000..5fed9212a
--- /dev/null
+++ b/toolkit/components/jsdownloads/src/DownloadIntegration.jsm
@@ -0,0 +1,1273 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* 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/. */
+
+/**
+ * Provides functions to integrate with the host application, handling for
+ * example the global prompts on shutdown.
+ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "DownloadIntegration",
+];
+
+////////////////////////////////////////////////////////////////////////////////
+//// Globals
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+const Cr = Components.results;
+
+Cu.import("resource://gre/modules/Integration.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "AsyncShutdown",
+                                  "resource://gre/modules/AsyncShutdown.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DeferredTask",
+                                  "resource://gre/modules/DeferredTask.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Downloads",
+                                  "resource://gre/modules/Downloads.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadStore",
+                                  "resource://gre/modules/DownloadStore.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadImport",
+                                  "resource://gre/modules/DownloadImport.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadUIHelper",
+                                  "resource://gre/modules/DownloadUIHelper.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
+                                  "resource://gre/modules/FileUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
+                                  "resource://gre/modules/NetUtil.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "OS",
+                                  "resource://gre/modules/osfile.jsm");
+#ifdef MOZ_PLACES
+XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils",
+                                  "resource://gre/modules/PlacesUtils.jsm");
+#endif
+XPCOMUtils.defineLazyModuleGetter(this, "Promise",
+                                  "resource://gre/modules/Promise.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Services",
+                                  "resource://gre/modules/Services.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+                                  "resource://gre/modules/Task.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
+                                  "resource://gre/modules/NetUtil.jsm");
+
+XPCOMUtils.defineLazyServiceGetter(this, "gDownloadPlatform",
+                                   "@mozilla.org/toolkit/download-platform;1",
+                                   "mozIDownloadPlatform");
+XPCOMUtils.defineLazyServiceGetter(this, "gEnvironment",
+                                   "@mozilla.org/process/environment;1",
+                                   "nsIEnvironment");
+XPCOMUtils.defineLazyServiceGetter(this, "gMIMEService",
+                                   "@mozilla.org/mime;1",
+                                   "nsIMIMEService");
+XPCOMUtils.defineLazyServiceGetter(this, "gExternalProtocolService",
+                                   "@mozilla.org/uriloader/external-protocol-service;1",
+                                   "nsIExternalProtocolService");
+#ifdef MOZ_WIDGET_ANDROID
+XPCOMUtils.defineLazyModuleGetter(this, "RuntimePermissions",
+                                  "resource://gre/modules/RuntimePermissions.jsm");
+#endif
+
+XPCOMUtils.defineLazyGetter(this, "gParentalControlsService", function() {
+  if ("@mozilla.org/parental-controls-service;1" in Cc) {
+    return Cc["@mozilla.org/parental-controls-service;1"]
+      .createInstance(Ci.nsIParentalControlsService);
+  }
+  return null;
+});
+
+XPCOMUtils.defineLazyServiceGetter(this, "gApplicationReputationService",
+           "@mozilla.org/downloads/application-reputation-service;1",
+           Ci.nsIApplicationReputationService);
+
+XPCOMUtils.defineLazyServiceGetter(this, "volumeService",
+                                   "@mozilla.org/telephony/volume-service;1",
+                                   "nsIVolumeService");
+
+// We have to use the gCombinedDownloadIntegration identifier because, in this
+// module only, the DownloadIntegration identifier refers to the base version.
+Integration.downloads.defineModuleGetter(this, "gCombinedDownloadIntegration",
+            "resource://gre/modules/DownloadIntegration.jsm",
+            "DownloadIntegration");
+
+const Timer = Components.Constructor("@mozilla.org/timer;1", "nsITimer",
+                                     "initWithCallback");
+
+/**
+ * Indicates the delay between a change to the downloads data and the related
+ * save operation.
+ *
+ * For best efficiency, this value should be high enough that the input/output
+ * for opening or closing the target file does not overlap with the one for
+ * saving the list of downloads.
+ */
+const kSaveDelayMs = 1500;
+
+/**
+ * This pref indicates if we have already imported (or attempted to import)
+ * the downloads database from the previous SQLite storage.
+ */
+const kPrefImportedFromSqlite = "browser.download.importedFromSqlite";
+
+/**
+ * List of observers to listen against
+ */
+const kObserverTopics = [
+  "quit-application-requested",
+  "offline-requested",
+  "last-pb-context-exiting",
+  "last-pb-context-exited",
+  "sleep_notification",
+  "suspend_process_notification",
+  "wake_notification",
+  "resume_process_notification",
+  "network:offline-about-to-go-offline",
+  "network:offline-status-changed",
+  "xpcom-will-shutdown",
+];
+
+/**
+ * Maps nsIApplicationReputationService verdicts with the DownloadError ones.
+ */
+const kVerdictMap = {
+  [Ci.nsIApplicationReputationService.VERDICT_DANGEROUS]:
+                Downloads.Error.BLOCK_VERDICT_MALWARE,
+  [Ci.nsIApplicationReputationService.VERDICT_UNCOMMON]:
+                Downloads.Error.BLOCK_VERDICT_UNCOMMON,
+  [Ci.nsIApplicationReputationService.VERDICT_POTENTIALLY_UNWANTED]:
+                Downloads.Error.BLOCK_VERDICT_POTENTIALLY_UNWANTED,
+  [Ci.nsIApplicationReputationService.VERDICT_DANGEROUS_HOST]:
+                Downloads.Error.BLOCK_VERDICT_MALWARE,
+};
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadIntegration
+
+/**
+ * Provides functions to integrate with the host application, handling for
+ * example the global prompts on shutdown.
+ */
+this.DownloadIntegration = {
+  /**
+   * Main DownloadStore object for loading and saving the list of persistent
+   * downloads, or null if the download list was never requested and thus it
+   * doesn't need to be persisted.
+   */
+  _store: null,
+
+  /**
+   * Returns whether data for blocked downloads should be kept on disk.
+   * Implementations which support unblocking downloads may return true to
+   * keep the blocked download on disk until its fate is decided.
+   *
+   * If a download is blocked and the partial data is kept the Download's
+   * 'hasBlockedData' property will be true. In this state Download.unblock()
+   * or Download.confirmBlock() may be used to either unblock the download or
+   * remove the downloaded data respectively.
+   *
+   * Even if shouldKeepBlockedData returns true, if the download did not use a
+   * partFile the blocked data will be removed - preventing the complete
+   * download from existing on disk with its final filename.
+   *
+   * @return boolean True if data should be kept.
+   */
+  shouldKeepBlockedData() {
+    const FIREFOX_ID = "{ec8030f7-c20a-464f-9b0e-13a3a9e97384}";
+    return Services.appinfo.ID == FIREFOX_ID;
+  },
+
+  /**
+   * Performs initialization of the list of persistent downloads, before its
+   * first use by the host application.  This function may be called only once
+   * during the entire lifetime of the application.
+   *
+   * @param list
+   *        DownloadList object to be initialized.
+   *
+   * @return {Promise}
+   * @resolves When the list has been initialized.
+   * @rejects JavaScript exception.
+   */
+  initializePublicDownloadList: Task.async(function* (list) {
+    try {
+      yield this.loadPublicDownloadListFromStore(list);
+    } catch (ex) {
+      Cu.reportError(ex);
+    }
+
+    // After the list of persistent downloads has been loaded, we can add the
+    // history observers, even if the load operation failed. This object is kept
+    // alive by the history service.
+    new DownloadHistoryObserver(list);
+  }),
+
+  /**
+   * Called by initializePublicDownloadList to load the list of persistent
+   * downloads, before its first use by the host application.  This function may
+   * be called only once during the entire lifetime of the application.
+   *
+   * @param list
+   *        DownloadList object to be populated with the download objects
+   *        serialized from the previous session.  This list will be persisted
+   *        to disk during the session lifetime.
+   *
+   * @return {Promise}
+   * @resolves When the list has been populated.
+   * @rejects JavaScript exception.
+   */
+  loadPublicDownloadListFromStore: Task.async(function* (list) {
+    if (this._store) {
+      throw new Error("Initialization may be performed only once.");
+    }
+
+    this._store = new DownloadStore(list, OS.Path.join(
+                                             OS.Constants.Path.profileDir,
+                                             "downloads.json"));
+    this._store.onsaveitem = this.shouldPersistDownload.bind(this);
+
+    try {
+      if (this._importedFromSqlite) {
+        yield this._store.load();
+      } else {
+        let sqliteDBpath = OS.Path.join(OS.Constants.Path.profileDir,
+                                        "downloads.sqlite");
+
+        if (yield OS.File.exists(sqliteDBpath)) {
+          let sqliteImport = new DownloadImport(list, sqliteDBpath);
+          yield sqliteImport.import();
+
+          let importCount = (yield list.getAll()).length;
+          if (importCount > 0) {
+            try {
+              yield this._store.save();
+            } catch (ex) { }
+          }
+
+          // No need to wait for the file removal.
+          OS.File.remove(sqliteDBpath).then(null, Cu.reportError);
+        }
+
+        Services.prefs.setBoolPref(kPrefImportedFromSqlite, true);
+
+        // Don't even report error here because this file is pre Firefox 3
+        // and most likely doesn't exist.
+        OS.File.remove(OS.Path.join(OS.Constants.Path.profileDir,
+                                    "downloads.rdf")).catch(() => {});
+
+      }
+    } catch (ex) {
+      Cu.reportError(ex);
+    }
+
+    // Add the view used for detecting changes to downloads to be persisted.
+    // We must do this after the list of persistent downloads has been loaded,
+    // even if the load operation failed. We wait for a complete initialization
+    // so other callers cannot modify the list without being detected. The
+    // DownloadAutoSaveView is kept alive by the underlying DownloadList.
+    yield new DownloadAutoSaveView(list, this._store).initialize();
+  }),
+
+  /**
+   * Determines if a Download object from the list of persistent downloads
+   * should be saved into a file, so that it can be restored across sessions.
+   *
+   * This function allows filtering out downloads that the host application is
+   * not interested in persisting across sessions, for example downloads that
+   * finished successfully.
+   *
+   * @param aDownload
+   *        The Download object to be inspected.  This is originally taken from
+   *        the global DownloadList object for downloads that were not started
+   *        from a private browsing window.  The item may have been removed
+   *        from the list since the save operation started, though in this case
+   *        the save operation will be repeated later.
+   *
+   * @return True to save the download, false otherwise.
+   */
+  shouldPersistDownload(aDownload) {
+    // On all platforms, we save all the downloads currently in progress, as
+    // well as stopped downloads for which we retained partially downloaded
+    // data or we have blocked data.
+    if (!aDownload.stopped || aDownload.hasPartialData ||
+        aDownload.hasBlockedData) {
+      return true;
+    }
+#ifdef MOZ_B2G
+    // On B2G we keep a few days of history.
+    let maxTime = Date.now() -
+      Services.prefs.getIntPref("dom.downloads.max_retention_days") * 24 * 60 * 60 * 1000;
+    return aDownload.startTime > maxTime;
+#elif defined(MOZ_WIDGET_ANDROID)
+    // On Android we store all history.
+    return true;
+#else
+    // On Desktop, stopped downloads for which we don't need to track the
+    // presence of a ".part" file are only retained in the browser history.
+    return false;
+#endif
+  },
+
+  /**
+   * Returns the system downloads directory asynchronously.
+   *
+   * @return {Promise}
+   * @resolves The downloads directory string path.
+   */
+  getSystemDownloadsDirectory: Task.async(function* () {
+    if (this._downloadsDirectory) {
+      return this._downloadsDirectory;
+    }
+
+    let directoryPath = null;
+#ifdef XP_MACOSX
+    directoryPath = this._getDirectory("DfltDwnld");
+#elifdef XP_WIN
+    // For XP/2K, use My Documents/Downloads. Other version uses
+    // the default Downloads directory.
+    let version = parseFloat(Services.sysinfo.getProperty("version"));
+    if (version < 6) {
+      directoryPath = yield this._createDownloadsDirectory("Pers");
+    } else {
+      directoryPath = this._getDirectory("DfltDwnld");
+    }
+#elifdef XP_UNIX
+#ifdef MOZ_WIDGET_ANDROID
+    // Android doesn't have a $HOME directory, and by default we only have
+    // write access to /data/data/org.mozilla.{$APP} and /sdcard
+    directoryPath = gEnvironment.get("DOWNLOADS_DIRECTORY");
+    if (!directoryPath) {
+      throw new Components.Exception("DOWNLOADS_DIRECTORY is not set.",
+                                     Cr.NS_ERROR_FILE_UNRECOGNIZED_PATH);
+    }
+#else
+    // For Linux, use XDG download dir, with a fallback to Home/Downloads
+    // if the XDG user dirs are disabled.
+    try {
+      directoryPath = this._getDirectory("DfltDwnld");
+    } catch(e) {
+      directoryPath = yield this._createDownloadsDirectory("Home");
+    }
+#endif
+#else
+    directoryPath = yield this._createDownloadsDirectory("Home");
+#endif
+
+    this._downloadsDirectory = directoryPath;
+    return this._downloadsDirectory;
+  }),
+  _downloadsDirectory: null,
+
+  /**
+   * Returns the user downloads directory asynchronously.
+   *
+   * @return {Promise}
+   * @resolves The downloads directory string path.
+   */
+  getPreferredDownloadsDirectory: Task.async(function* () {
+    let directoryPath = null;
+    let prefValue = 1;
+
+    try {
+      prefValue = Services.prefs.getIntPref("browser.download.folderList");
+    } catch(e) {}
+
+    switch(prefValue) {
+      case 0: // Desktop
+        directoryPath = this._getDirectory("Desk");
+        break;
+      case 1: // Downloads
+        directoryPath = yield this.getSystemDownloadsDirectory();
+        break;
+      case 2: // Custom
+        try {
+          let directory = Services.prefs.getComplexValue("browser.download.dir",
+                                                         Ci.nsIFile);
+          directoryPath = directory.path;
+          yield OS.File.makeDir(directoryPath, { ignoreExisting: true });
+        } catch(ex) {
+          // Either the preference isn't set or the directory cannot be created.
+          directoryPath = yield this.getSystemDownloadsDirectory();
+        }
+        break;
+      default:
+        directoryPath = yield this.getSystemDownloadsDirectory();
+    }
+    return directoryPath;
+  }),
+
+  /**
+   * Returns the temporary downloads directory asynchronously.
+   *
+   * @return {Promise}
+   * @resolves The downloads directory string path.
+   */
+  getTemporaryDownloadsDirectory: Task.async(function* () {
+    let directoryPath = null;
+#ifdef XP_MACOSX
+    directoryPath = yield this.getPreferredDownloadsDirectory();
+#elifdef MOZ_WIDGET_ANDROID
+    directoryPath = yield this.getSystemDownloadsDirectory();
+#elifdef MOZ_WIDGET_GONK
+    directoryPath = yield this.getSystemDownloadsDirectory();
+#else
+    directoryPath = this._getDirectory("TmpD");
+#endif
+    return directoryPath;
+  }),
+
+  /**
+   * Checks to determine whether to block downloads for parental controls.
+   *
+   * aParam aDownload
+   *        The download object.
+   *
+   * @return {Promise}
+   * @resolves The boolean indicates to block downloads or not.
+   */
+  shouldBlockForParentalControls(aDownload) {
+    let isEnabled = gParentalControlsService &&
+                    gParentalControlsService.parentalControlsEnabled;
+    let shouldBlock = isEnabled &&
+                      gParentalControlsService.blockFileDownloadsEnabled;
+
+    // Log the event if required by parental controls settings.
+    if (isEnabled && gParentalControlsService.loggingEnabled) {
+      gParentalControlsService.log(gParentalControlsService.ePCLog_FileDownload,
+                                   shouldBlock,
+                                   NetUtil.newURI(aDownload.source.url), null);
+    }
+
+    return Promise.resolve(shouldBlock);
+  },
+
+  /**
+   * Checks to determine whether to block downloads for not granted runtime permissions.
+   *
+   * @return {Promise}
+   * @resolves The boolean indicates to block downloads or not.
+   */
+  shouldBlockForRuntimePermissions() {
+#ifdef MOZ_WIDGET_ANDROID
+    return RuntimePermissions.waitForPermissions(RuntimePermissions.WRITE_EXTERNAL_STORAGE)
+                             .then(permissionGranted => !permissionGranted);
+#else
+    return Promise.resolve(false);
+#endif
+  },
+
+  /**
+   * Checks to determine whether to block downloads because they might be
+   * malware, based on application reputation checks.
+   *
+   * aParam aDownload
+   *        The download object.
+   *
+   * @return {Promise}
+   * @resolves Object with the following properties:
+   *           {
+   *             shouldBlock: Whether the download should be blocked.
+   *             verdict: Detailed reason for the block, according to the
+   *                      "Downloads.Error.BLOCK_VERDICT_" constants, or empty
+   *                      string if the reason is unknown.
+   *           }
+   */
+  shouldBlockForReputationCheck(aDownload) {
+    let hash;
+    let sigInfo;
+    let channelRedirects;
+    try {
+      hash = aDownload.saver.getSha256Hash();
+      sigInfo = aDownload.saver.getSignatureInfo();
+      channelRedirects = aDownload.saver.getRedirects();
+    } catch (ex) {
+      // Bail if DownloadSaver doesn't have a hash or signature info.
+      return Promise.resolve({
+        shouldBlock: false,
+        verdict: "",
+      });
+    }
+    if (!hash || !sigInfo) {
+      return Promise.resolve({
+        shouldBlock: false,
+        verdict: "",
+      });
+    }
+    let deferred = Promise.defer();
+    let aReferrer = null;
+    if (aDownload.source.referrer) {
+      aReferrer = NetUtil.newURI(aDownload.source.referrer);
+    }
+    gApplicationReputationService.queryReputation({
+      sourceURI: NetUtil.newURI(aDownload.source.url),
+      referrerURI: aReferrer,
+      fileSize: aDownload.currentBytes,
+      sha256Hash: hash,
+      suggestedFileName: OS.Path.basename(aDownload.target.path),
+      signatureInfo: sigInfo,
+      redirects: channelRedirects },
+      function onComplete(aShouldBlock, aRv, aVerdict) {
+        deferred.resolve({
+          shouldBlock: aShouldBlock,
+          verdict: (aShouldBlock && kVerdictMap[aVerdict]) || "",
+        });
+      });
+    return deferred.promise;
+  },
+
+#ifdef XP_WIN
+  /**
+   * Checks whether downloaded files should be marked as coming from
+   * Internet Zone.
+   *
+   * @return true if files should be marked
+   */
+  _shouldSaveZoneInformation() {
+    let key = Cc["@mozilla.org/windows-registry-key;1"]
+                .createInstance(Ci.nsIWindowsRegKey);
+    try {
+      key.open(Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+               "Software\\Microsoft\\Windows\\CurrentVersion\\Policies\\Attachments",
+               Ci.nsIWindowsRegKey.ACCESS_QUERY_VALUE);
+      try {
+        return key.readIntValue("SaveZoneInformation") != 1;
+      } finally {
+        key.close();
+      }
+    } catch (ex) {
+      // If the key is not present, files should be marked by default.
+      return true;
+    }
+  },
+#endif
+
+  /**
+   * Performs platform-specific operations when a download is done.
+   *
+   * aParam aDownload
+   *        The Download object.
+   *
+   * @return {Promise}
+   * @resolves When all the operations completed successfully.
+   * @rejects JavaScript exception if any of the operations failed.
+   */
+  downloadDone: Task.async(function* (aDownload) {
+#ifdef XP_WIN
+    // On Windows, we mark any file saved to the NTFS file system as coming
+    // from the Internet security zone unless Group Policy disables the
+    // feature.  We do this by writing to the "Zone.Identifier" Alternate
+    // Data Stream directly, because the Save method of the
+    // IAttachmentExecute interface would trigger operations that may cause
+    // the application to hang, or other performance issues.
+    // The stream created in this way is forward-compatible with all the
+    // current and future versions of Windows.
+    if (this._shouldSaveZoneInformation()) {
+      let zone;
+      try {
+        zone = gDownloadPlatform.mapUrlToZone(aDownload.source.url);
+      } catch (e) {
+        // Default to Internet Zone if mapUrlToZone failed for
+        // whatever reason.
+        zone = Ci.mozIDownloadPlatform.ZONE_INTERNET;
+      }
+      try {
+        // Don't write zone IDs for Local, Intranet, or Trusted sites
+        // to match Windows behavior.
+        if (zone >= Ci.mozIDownloadPlatform.ZONE_INTERNET) {
+          let streamPath = aDownload.target.path + ":Zone.Identifier";
+          let stream = yield OS.File.open(
+            streamPath,
+            { create: true },
+            { winAllowLengthBeyondMaxPathWithCaveats: true }
+          );
+          try {
+            yield stream.write(new TextEncoder().encode("[ZoneTransfer]\r\nZoneId=" + zone + "\r\n"));
+          } finally {
+            yield stream.close();
+          }
+        }
+      } catch (ex) {
+        // If writing to the stream fails, we ignore the error and continue.
+        // The Windows API error 123 (ERROR_INVALID_NAME) is expected to
+        // occur when working on a file system that does not support
+        // Alternate Data Streams, like FAT32, thus we don't report this
+        // specific error.
+        if (!(ex instanceof OS.File.Error) || ex.winLastError != 123) {
+          Cu.reportError(ex);
+        }
+      }
+    }
+#endif
+
+    // The file with the partially downloaded data has restrictive permissions
+    // that don't allow other users on the system to access it.  Now that the
+    // download is completed, we need to adjust permissions based on whether
+    // this is a permanently downloaded file or a temporary download to be
+    // opened read-only with an external application.
+    try {
+      // The following logic to determine whether this is a temporary download
+      // is due to the fact that "deleteTempFileOnExit" is false on Mac, where
+      // downloads to be opened with external applications are preserved in
+      // the "Downloads" folder like normal downloads.
+      let isTemporaryDownload =
+        aDownload.launchWhenSucceeded && (aDownload.source.isPrivate ||
+        Services.prefs.getBoolPref("browser.helperApps.deleteTempFileOnExit"));
+      // Permanently downloaded files are made accessible by other users on
+      // this system, while temporary downloads are marked as read-only.
+      let options = {};
+      if (isTemporaryDownload) {
+        options.unixMode = 0o400;
+        options.winAttributes = {readOnly: true};
+      } else {
+        options.unixMode = 0o666;
+      }
+      // On Unix, the umask of the process is respected.
+      yield OS.File.setPermissions(aDownload.target.path, options);
+    } catch (ex) {
+      // We should report errors with making the permissions less restrictive
+      // or marking the file as read-only on Unix and Mac, but this should not
+      // prevent the download from completing.
+      // The setPermissions API error EPERM is expected to occur when working
+      // on a file system that does not support file permissions, like FAT32,
+      // thus we don't report this error.
+      if (!(ex instanceof OS.File.Error) || ex.unixErrno != OS.Constants.libc.EPERM) {
+        Cu.reportError(ex);
+      }
+    }
+
+    let aReferrer = null;
+    if (aDownload.source.referrer) {
+      aReferrer = NetUtil.newURI(aDownload.source.referrer);
+    }
+
+    gDownloadPlatform.downloadDone(NetUtil.newURI(aDownload.source.url),
+                                   aReferrer,
+                                   new FileUtils.File(aDownload.target.path),
+                                   aDownload.contentType,
+                                   aDownload.source.isPrivate);
+  }),
+
+  /**
+   * Launches a file represented by the target of a download. This can
+   * open the file with the default application for the target MIME type
+   * or file extension, or with a custom application if
+   * aDownload.launcherPath is set.
+   *
+   * @param    aDownload
+   *           A Download object that contains the necessary information
+   *           to launch the file. The relevant properties are: the target
+   *           file, the contentType and the custom application chosen
+   *           to launch it.
+   *
+   * @return {Promise}
+   * @resolves When the instruction to launch the file has been
+   *           successfully given to the operating system. Note that
+   *           the OS might still take a while until the file is actually
+   *           launched.
+   * @rejects  JavaScript exception if there was an error trying to launch
+   *           the file.
+   */
+  launchDownload: Task.async(function* (aDownload) {
+    let file = new FileUtils.File(aDownload.target.path);
+
+#ifndef XP_WIN
+    // Ask for confirmation if the file is executable, except on Windows where
+    // the operating system will show the prompt based on the security zone.
+    // We do this here, instead of letting the caller handle the prompt
+    // separately in the user interface layer, for two reasons.  The first is
+    // because of its security nature, so that add-ons cannot forget to do
+    // this check.  The second is that the system-level security prompt would
+    // be displayed at launch time in any case.
+    if (file.isExecutable() &&
+        !(yield this.confirmLaunchExecutable(file.path))) {
+      return;
+    }
+#endif
+
+    // In case of a double extension, like ".tar.gz", we only
+    // consider the last one, because the MIME service cannot
+    // handle multiple extensions.
+    let fileExtension = null, mimeInfo = null;
+    let match = file.leafName.match(/\.([^.]+)$/);
+    if (match) {
+      fileExtension = match[1];
+    }
+
+    try {
+      // The MIME service might throw if contentType == "" and it can't find
+      // a MIME type for the given extension, so we'll treat this case as
+      // an unknown mimetype.
+      mimeInfo = gMIMEService.getFromTypeAndExtension(aDownload.contentType,
+                                                      fileExtension);
+    } catch (e) { }
+
+    if (aDownload.launcherPath) {
+      if (!mimeInfo) {
+        // This should not happen on normal circumstances because launcherPath
+        // is only set when we had an instance of nsIMIMEInfo to retrieve
+        // the custom application chosen by the user.
+        throw new Error(
+          "Unable to create nsIMIMEInfo to launch a custom application");
+      }
+
+      // Custom application chosen
+      let localHandlerApp = Cc["@mozilla.org/uriloader/local-handler-app;1"]
+                              .createInstance(Ci.nsILocalHandlerApp);
+      localHandlerApp.executable = new FileUtils.File(aDownload.launcherPath);
+
+      mimeInfo.preferredApplicationHandler = localHandlerApp;
+      mimeInfo.preferredAction = Ci.nsIMIMEInfo.useHelperApp;
+
+      this.launchFile(file, mimeInfo);
+      return;
+    }
+
+    // No custom application chosen, let's launch the file with the default
+    // handler. First, let's try to launch it through the MIME service.
+    if (mimeInfo) {
+      mimeInfo.preferredAction = Ci.nsIMIMEInfo.useSystemDefault;
+
+      try {
+        this.launchFile(file, mimeInfo);
+        return;
+      } catch (ex) { }
+    }
+
+    // If it didn't work or if there was no MIME info available,
+    // let's try to directly launch the file.
+    try {
+      this.launchFile(file);
+      return;
+    } catch (ex) { }
+
+    // If our previous attempts failed, try sending it through
+    // the system's external "file:" URL handler.
+    gExternalProtocolService.loadUrl(NetUtil.newURI(file));
+  }),
+
+  /**
+   * Asks for confirmation for launching the specified executable file. This
+   * can be overridden by regression tests to avoid the interactive prompt.
+   */
+  confirmLaunchExecutable: Task.async(function* (path) {
+    // We don't anchor the prompt to a specific window intentionally, not
+    // only because this is the same behavior as the system-level prompt,
+    // but also because the most recently active window is the right choice
+    // in basically all cases.
+    return yield DownloadUIHelper.getPrompter().confirmLaunchExecutable(path);
+  }),
+
+  /**
+   * Launches the specified file, unless overridden by regression tests.
+   */
+  launchFile(file, mimeInfo) {
+    if (mimeInfo) {
+      mimeInfo.launchWithFile(file);
+    } else {
+      file.launch();
+    }
+  },
+
+  /**
+   * Shows the containing folder of a file.
+   *
+   * @param aFilePath
+   *        The path to the file.
+   *
+   * @return {Promise}
+   * @resolves When the instruction to open the containing folder has been
+   *           successfully given to the operating system. Note that
+   *           the OS might still take a while until the folder is actually
+   *           opened.
+   * @rejects  JavaScript exception if there was an error trying to open
+   *           the containing folder.
+   */
+  showContainingDirectory: Task.async(function* (aFilePath) {
+    let file = new FileUtils.File(aFilePath);
+
+    try {
+      // Show the directory containing the file and select the file.
+      file.reveal();
+      return;
+    } catch (ex) { }
+
+    // If reveal fails for some reason (e.g., it's not implemented on unix
+    // or the file doesn't exist), try using the parent if we have it.
+    let parent = file.parent;
+    if (!parent) {
+      throw new Error(
+        "Unexpected reference to a top-level directory instead of a file");
+    }
+
+    try {
+      // Open the parent directory to show where the file should be.
+      parent.launch();
+      return;
+    } catch (ex) { }
+
+    // If launch also fails (probably because it's not implemented), let
+    // the OS handler try to open the parent.
+    gExternalProtocolService.loadUrl(NetUtil.newURI(parent));
+  }),
+
+  /**
+   * Calls the directory service, create a downloads directory and returns an
+   * nsIFile for the downloads directory.
+   *
+   * @return {Promise}
+   * @resolves The directory string path.
+   */
+  _createDownloadsDirectory(aName) {
+    // We read the name of the directory from the list of translated strings
+    // that is kept by the UI helper module, even if this string is not strictly
+    // displayed in the user interface.
+    let directoryPath = OS.Path.join(this._getDirectory(aName),
+                                     DownloadUIHelper.strings.downloadsFolder);
+
+    // Create the Downloads folder and ignore if it already exists.
+    return OS.File.makeDir(directoryPath, { ignoreExisting: true })
+                  .then(() => directoryPath);
+  },
+
+  /**
+   * Returns the string path for the given directory service location name. This
+   * can be overridden by regression tests to return the path of the system
+   * temporary directory in all cases.
+   */
+  _getDirectory(name) {
+    return Services.dirsvc.get(name, Ci.nsIFile).path;
+  },
+
+  /**
+   * Register the downloads interruption observers.
+   *
+   * @param aList
+   *        The public or private downloads list.
+   * @param aIsPrivate
+   *        True if the list is private, false otherwise.
+   *
+   * @return {Promise}
+   * @resolves When the views and observers are added.
+   */
+  addListObservers(aList, aIsPrivate) {
+    DownloadObserver.registerView(aList, aIsPrivate);
+    if (!DownloadObserver.observersAdded) {
+      DownloadObserver.observersAdded = true;
+      for (let topic of kObserverTopics) {
+        Services.obs.addObserver(DownloadObserver, topic, false);
+      }
+    }
+    return Promise.resolve();
+  },
+
+  /**
+   * Force a save on _store if it exists. Used to ensure downloads do not
+   * persist after being sanitized on Android.
+   *
+   * @return {Promise}
+   * @resolves When _store.save() completes.
+   */
+  forceSave() {
+    if (this._store) {
+      return this._store.save();
+    }
+    return Promise.resolve();
+  },
+
+  /**
+   * Checks if we have already imported (or attempted to import)
+   * the downloads database from the previous SQLite storage.
+   *
+   * @return boolean True if we the previous DB was imported.
+   */
+  get _importedFromSqlite() {
+    try {
+      return Services.prefs.getBoolPref(kPrefImportedFromSqlite);
+    } catch (ex) {
+      return false;
+    }
+  },
+};
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadObserver
+
+this.DownloadObserver = {
+  /**
+   * Flag to determine if the observers have been added previously.
+   */
+  observersAdded: false,
+
+  /**
+   * Timer used to delay restarting canceled downloads upon waking and returning
+   * online.
+   */
+  _wakeTimer: null,
+
+  /**
+   * Set that contains the in progress publics downloads.
+   * It's kept updated when a public download is added, removed or changes its
+   * properties.
+   */
+  _publicInProgressDownloads: new Set(),
+
+  /**
+   * Set that contains the in progress private downloads.
+   * It's kept updated when a private download is added, removed or changes its
+   * properties.
+   */
+  _privateInProgressDownloads: new Set(),
+
+  /**
+   * Set that contains the downloads that have been canceled when going offline
+   * or to sleep. These are started again when returning online or waking. This
+   * list is not persisted so when exiting and restarting, the downloads will not
+   * be started again.
+   */
+  _canceledOfflineDownloads: new Set(),
+
+  /**
+   * Registers a view that updates the corresponding downloads state set, based
+   * on the aIsPrivate argument. The set is updated when a download is added,
+   * removed or changes its properties.
+   *
+   * @param aList
+   *        The public or private downloads list.
+   * @param aIsPrivate
+   *        True if the list is private, false otherwise.
+   */
+  registerView: function DO_registerView(aList, aIsPrivate) {
+    let downloadsSet = aIsPrivate ? this._privateInProgressDownloads
+                                  : this._publicInProgressDownloads;
+    let downloadsView = {
+      onDownloadAdded: aDownload => {
+        if (!aDownload.stopped) {
+          downloadsSet.add(aDownload);
+        }
+      },
+      onDownloadChanged: aDownload => {
+        if (aDownload.stopped) {
+          downloadsSet.delete(aDownload);
+        } else {
+          downloadsSet.add(aDownload);
+        }
+      },
+      onDownloadRemoved: aDownload => {
+        downloadsSet.delete(aDownload);
+        // The download must also be removed from the canceled when offline set.
+        this._canceledOfflineDownloads.delete(aDownload);
+      }
+    };
+
+    // We register the view asynchronously.
+    aList.addView(downloadsView).then(null, Cu.reportError);
+  },
+
+  /**
+   * Wrapper that handles the test mode before calling the prompt that display
+   * a warning message box that informs that there are active downloads,
+   * and asks whether the user wants to cancel them or not.
+   *
+   * @param aCancel
+   *        The observer notification subject.
+   * @param aDownloadsCount
+   *        The current downloads count.
+   * @param aPrompter
+   *        The prompter object that shows the confirm dialog.
+   * @param aPromptType
+   *        The type of prompt notification depending on the observer.
+   */
+  _confirmCancelDownloads: function DO_confirmCancelDownload(
+    aCancel, aDownloadsCount, aPrompter, aPromptType) {
+    // If user has already dismissed the request, then do nothing.
+    if ((aCancel instanceof Ci.nsISupportsPRBool) && aCancel.data) {
+      return;
+    }
+    // Handle test mode
+    if (gCombinedDownloadIntegration._testPromptDownloads) {
+      gCombinedDownloadIntegration._testPromptDownloads = aDownloadsCount;
+      return;
+    }
+
+    aCancel.data = aPrompter.confirmCancelDownloads(aDownloadsCount, aPromptType);
+  },
+
+  /**
+   * Resume all downloads that were paused when going offline, used when waking
+   * from sleep or returning from being offline.
+   */
+  _resumeOfflineDownloads: function DO_resumeOfflineDownloads() {
+    this._wakeTimer = null;
+
+    for (let download of this._canceledOfflineDownloads) {
+      download.start().catch(() => {});
+    }
+  },
+
+  ////////////////////////////////////////////////////////////////////////////
+  //// nsIObserver
+
+  observe: function DO_observe(aSubject, aTopic, aData) {
+    let downloadsCount;
+    let p = DownloadUIHelper.getPrompter();
+    switch (aTopic) {
+      case "quit-application-requested":
+        downloadsCount = this._publicInProgressDownloads.size +
+                         this._privateInProgressDownloads.size;
+        this._confirmCancelDownloads(aSubject, downloadsCount, p, p.ON_QUIT);
+        break;
+      case "offline-requested":
+        downloadsCount = this._publicInProgressDownloads.size +
+                         this._privateInProgressDownloads.size;
+        this._confirmCancelDownloads(aSubject, downloadsCount, p, p.ON_OFFLINE);
+        break;
+      case "last-pb-context-exiting":
+        downloadsCount = this._privateInProgressDownloads.size;
+        this._confirmCancelDownloads(aSubject, downloadsCount, p,
+                                     p.ON_LEAVE_PRIVATE_BROWSING);
+        break;
+      case "last-pb-context-exited":
+        let promise = Task.spawn(function() {
+          let list = yield Downloads.getList(Downloads.PRIVATE);
+          let downloads = yield list.getAll();
+
+          // We can remove the downloads and finalize them in parallel.
+          for (let download of downloads) {
+            list.remove(download).then(null, Cu.reportError);
+            download.finalize(true).then(null, Cu.reportError);
+          }
+        });
+        // Handle test mode
+        if (gCombinedDownloadIntegration._testResolveClearPrivateList) {
+          gCombinedDownloadIntegration._testResolveClearPrivateList(promise);
+        } else {
+          promise.catch(ex => Cu.reportError(ex));
+        }
+        break;
+      case "sleep_notification":
+      case "suspend_process_notification":
+      case "network:offline-about-to-go-offline":
+        for (let download of this._publicInProgressDownloads) {
+          download.cancel();
+          this._canceledOfflineDownloads.add(download);
+        }
+        for (let download of this._privateInProgressDownloads) {
+          download.cancel();
+          this._canceledOfflineDownloads.add(download);
+        }
+        break;
+      case "wake_notification":
+      case "resume_process_notification":
+        let wakeDelay = 10000;
+        try {
+          wakeDelay = Services.prefs.getIntPref("browser.download.manager.resumeOnWakeDelay");
+        } catch(e) {}
+
+        if (wakeDelay >= 0) {
+          this._wakeTimer = new Timer(this._resumeOfflineDownloads.bind(this), wakeDelay,
+                                      Ci.nsITimer.TYPE_ONE_SHOT);
+        }
+        break;
+      case "network:offline-status-changed":
+        if (aData == "online") {
+          this._resumeOfflineDownloads();
+        }
+        break;
+      // We need to unregister observers explicitly before we reach the
+      // "xpcom-shutdown" phase, otherwise observers may be notified when some
+      // required services are not available anymore. We can't unregister
+      // observers on "quit-application", because this module is also loaded
+      // during "make package" automation, and the quit notification is not sent
+      // in that execution environment (bug 973637).
+      case "xpcom-will-shutdown":
+        for (let topic of kObserverTopics) {
+          Services.obs.removeObserver(this, topic);
+        }
+        break;
+    }
+  },
+
+  ////////////////////////////////////////////////////////////////////////////
+  //// nsISupports
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver])
+};
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadHistoryObserver
+
+#ifdef MOZ_PLACES
+/**
+ * Registers a Places observer so that operations on download history are
+ * reflected on the provided list of downloads.
+ *
+ * You do not need to keep a reference to this object in order to keep it alive,
+ * because the history service already keeps a strong reference to it.
+ *
+ * @param aList
+ *        DownloadList object linked to this observer.
+ */
+this.DownloadHistoryObserver = function (aList)
+{
+  this._list = aList;
+  PlacesUtils.history.addObserver(this, false);
+}
+
+this.DownloadHistoryObserver.prototype = {
+  /**
+   * DownloadList object linked to this observer.
+   */
+  _list: null,
+
+  ////////////////////////////////////////////////////////////////////////////
+  //// nsISupports
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsINavHistoryObserver]),
+
+  ////////////////////////////////////////////////////////////////////////////
+  //// nsINavHistoryObserver
+
+  onDeleteURI: function DL_onDeleteURI(aURI, aGUID) {
+    this._list.removeFinished(download => aURI.equals(NetUtil.newURI(
+                                                      download.source.url)));
+  },
+
+  onClearHistory: function DL_onClearHistory() {
+    this._list.removeFinished();
+  },
+
+  onTitleChanged: function () {},
+  onBeginUpdateBatch: function () {},
+  onEndUpdateBatch: function () {},
+  onVisit: function () {},
+  onPageChanged: function () {},
+  onDeleteVisits: function () {},
+};
+#else
+/**
+ * Empty implementation when we have no Places support, for example on B2G.
+ */
+this.DownloadHistoryObserver = function (aList) {}
+#endif
+
+////////////////////////////////////////////////////////////////////////////////
+//// DownloadAutoSaveView
+
+/**
+ * This view can be added to a DownloadList object to trigger a save operation
+ * in the given DownloadStore object when a relevant change occurs.  You should
+ * call the "initialize" method in order to register the view and load the
+ * current state from disk.
+ *
+ * You do not need to keep a reference to this object in order to keep it alive,
+ * because the DownloadList object already keeps a strong reference to it.
+ *
+ * @param aList
+ *        The DownloadList object on which the view should be registered.
+ * @param aStore
+ *        The DownloadStore object used for saving.
+ */
+this.DownloadAutoSaveView = function (aList, aStore)
+{
+  this._list = aList;
+  this._store = aStore;
+  this._downloadsMap = new Map();
+  this._writer = new DeferredTask(() => this._store.save(), kSaveDelayMs);
+  AsyncShutdown.profileBeforeChange.addBlocker("DownloadAutoSaveView: writing data",
+                                               () => this._writer.finalize());
+}
+
+this.DownloadAutoSaveView.prototype = {
+  /**
+   * DownloadList object linked to this view.
+   */
+  _list: null,
+
+  /**
+   * The DownloadStore object used for saving.
+   */
+  _store: null,
+
+  /**
+   * True when the initial state of the downloads has been loaded.
+   */
+  _initialized: false,
+
+  /**
+   * Registers the view and loads the current state from disk.
+   *
+   * @return {Promise}
+   * @resolves When the view has been registered.
+   * @rejects JavaScript exception.
+   */
+  initialize: function ()
+  {
+    // We set _initialized to true after adding the view, so that
+    // onDownloadAdded doesn't cause a save to occur.
+    return this._list.addView(this).then(() => this._initialized = true);
+  },
+
+  /**
+   * This map contains only Download objects that should be saved to disk, and
+   * associates them with the result of their getSerializationHash function, for
+   * the purpose of detecting changes to the relevant properties.
+   */
+  _downloadsMap: null,
+
+  /**
+   * DeferredTask for the save operation.
+   */
+  _writer: null,
+
+  /**
+   * Called when the list of downloads changed, this triggers the asynchronous
+   * serialization of the list of downloads.
+   */
+  saveSoon: function ()
+  {
+    this._writer.arm();
+  },
+
+  //////////////////////////////////////////////////////////////////////////////
+  //// DownloadList view
+
+  onDownloadAdded: function (aDownload)
+  {
+    if (gCombinedDownloadIntegration.shouldPersistDownload(aDownload)) {
+      this._downloadsMap.set(aDownload, aDownload.getSerializationHash());
+      if (this._initialized) {
+        this.saveSoon();
+      }
+    }
+  },
+
+  onDownloadChanged: function (aDownload)
+  {
+    if (!gCombinedDownloadIntegration.shouldPersistDownload(aDownload)) {
+      if (this._downloadsMap.has(aDownload)) {
+        this._downloadsMap.delete(aDownload);
+        this.saveSoon();
+      }
+      return;
+    }
+
+    let hash = aDownload.getSerializationHash();
+    if (this._downloadsMap.get(aDownload) != hash) {
+      this._downloadsMap.set(aDownload, hash);
+      this.saveSoon();
+    }
+  },
+
+  onDownloadRemoved: function (aDownload)
+  {
+    if (this._downloadsMap.has(aDownload)) {
+      this._downloadsMap.delete(aDownload);
+      this.saveSoon();
+    }
+  },
+};
diff --git a/toolkit/components/jsdownloads/src/DownloadLegacy.js b/toolkit/components/jsdownloads/src/DownloadLegacy.js
new file mode 100644
index 000000000..fc9fb35d2
--- /dev/null
+++ b/toolkit/components/jsdownloads/src/DownloadLegacy.js
@@ -0,0 +1,309 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/**
+ * This component implements the XPCOM interfaces required for integration with
+ * the legacy download components.
+ *
+ * New code is expected to use the "Downloads.jsm" module directly, without
+ * going through the interfaces implemented in this XPCOM component.  These
+ * interfaces are only maintained for backwards compatibility with components
+ * that still work synchronously on the main thread.
+ */
+
+"use strict";
+
+// Globals
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+const Cr = Components.results;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "Downloads",
+                                  "resource://gre/modules/Downloads.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Promise",
+                                  "resource://gre/modules/Promise.jsm");
+
+// DownloadLegacyTransfer
+
+/**
+ * nsITransfer implementation that provides a bridge to a Download object.
+ *
+ * Legacy downloads work differently than the JavaScript implementation.  In the
+ * latter, the caller only provides the properties for the Download object and
+ * the entire process is handled by the "start" method.  In the legacy
+ * implementation, the caller must create a separate object to execute the
+ * download, and then make the download visible to the user by hooking it up to
+ * an nsITransfer instance.
+ *
+ * Since nsITransfer instances may be created before the download system is
+ * initialized, and initialization as well as other operations are asynchronous,
+ * this implementation is able to delay all progress and status notifications it
+ * receives until the associated Download object is finally created.
+ *
+ * Conversely, the DownloadLegacySaver object can also receive execution and
+ * cancellation requests asynchronously, before or after it is connected to
+ * this nsITransfer instance.  For that reason, those requests are communicated
+ * in a potentially deferred way, using promise objects.
+ *
+ * The component that executes the download implements nsICancelable to receive
+ * cancellation requests, but after cancellation it cannot be reused again.
+ *
+ * Since the components that execute the download may be different and they
+ * don't always give consistent results, this bridge takes care of enforcing the
+ * expectations, for example by ensuring the target file exists when the
+ * download is successful, even if the source has a size of zero bytes.
+ */
+function DownloadLegacyTransfer()
+{
+  this._deferDownload = Promise.defer();
+}
+
+DownloadLegacyTransfer.prototype = {
+  classID: Components.ID("{1b4c85df-cbdd-4bb6-b04e-613caece083c}"),
+
+  // nsISupports
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIWebProgressListener,
+                                         Ci.nsIWebProgressListener2,
+                                         Ci.nsITransfer]),
+
+  // nsIWebProgressListener
+
+  onStateChange: function DLT_onStateChange(aWebProgress, aRequest, aStateFlags,
+                                            aStatus)
+  {
+    if (!Components.isSuccessCode(aStatus)) {
+      this._componentFailed = true;
+    }
+
+    if ((aStateFlags & Ci.nsIWebProgressListener.STATE_START) &&
+        (aStateFlags & Ci.nsIWebProgressListener.STATE_IS_NETWORK)) {
+
+      let blockedByParentalControls = false;
+      // If it is a failed download, aRequest.responseStatus doesn't exist.
+      // (missing file on the server, network failure to download)
+      try {
+        // If the request's response has been blocked by Windows Parental Controls
+        // with an HTTP 450 error code, we must cancel the request synchronously.
+        blockedByParentalControls = aRequest instanceof Ci.nsIHttpChannel &&
+                                      aRequest.responseStatus == 450;
+      } catch (e) {
+        if (e.result == Cr.NS_ERROR_NOT_AVAILABLE) {
+          aRequest.cancel(Cr.NS_BINDING_ABORTED);
+        }
+      }
+
+      if (blockedByParentalControls) {
+        aRequest.cancel(Cr.NS_BINDING_ABORTED);
+      }
+
+      // The main request has just started.  Wait for the associated Download
+      // object to be available before notifying.
+      this._deferDownload.promise.then(download => {
+        // If the request was blocked, now that we have the download object we
+        // should set a flag that can be retrieved later when handling the
+        // cancellation so that the proper error can be thrown.
+        if (blockedByParentalControls) {
+          download._blockedByParentalControls = true;
+        }
+
+        download.saver.onTransferStarted(
+                         aRequest,
+                         this._cancelable instanceof Ci.nsIHelperAppLauncher);
+
+        // To handle asynchronous cancellation properly, we should hook up the
+        // handler only after we have been notified that the main request
+        // started.  We will wait until the main request stopped before
+        // notifying that the download has been canceled.  Since the request has
+        // not completed yet, deferCanceled is guaranteed to be set.
+        return download.saver.deferCanceled.promise.then(() => {
+          // Only cancel if the object executing the download is still running.
+          if (this._cancelable && !this._componentFailed) {
+            this._cancelable.cancel(Cr.NS_ERROR_ABORT);
+            if (this._cancelable instanceof Ci.nsIWebBrowserPersist) {
+              // This component will not send the STATE_STOP notification.
+              download.saver.onTransferFinished(aRequest, Cr.NS_ERROR_ABORT);
+              this._cancelable = null;
+            }
+          }
+        });
+      }).then(null, Cu.reportError);
+    } else if ((aStateFlags & Ci.nsIWebProgressListener.STATE_STOP) &&
+        (aStateFlags & Ci.nsIWebProgressListener.STATE_IS_NETWORK)) {
+      // The last file has been received, or the download failed.  Wait for the
+      // associated Download object to be available before notifying.
+      this._deferDownload.promise.then(download => {
+        // At this point, the hash has been set and we need to copy it to the
+        // DownloadSaver.
+        if (Components.isSuccessCode(aStatus)) {
+          download.saver.setSha256Hash(this._sha256Hash);
+          download.saver.setSignatureInfo(this._signatureInfo);
+          download.saver.setRedirects(this._redirects);
+        }
+        download.saver.onTransferFinished(aRequest, aStatus);
+      }).then(null, Cu.reportError);
+
+      // Release the reference to the component executing the download.
+      this._cancelable = null;
+    }
+  },
+
+  onProgressChange: function DLT_onProgressChange(aWebProgress, aRequest,
+                                                  aCurSelfProgress,
+                                                  aMaxSelfProgress,
+                                                  aCurTotalProgress,
+                                                  aMaxTotalProgress)
+  {
+    this.onProgressChange64(aWebProgress, aRequest, aCurSelfProgress,
+                            aMaxSelfProgress, aCurTotalProgress,
+                            aMaxTotalProgress);
+  },
+
+  onLocationChange: function () { },
+
+  onStatusChange: function DLT_onStatusChange(aWebProgress, aRequest, aStatus,
+                                              aMessage)
+  {
+    // The status change may optionally be received in addition to the state
+    // change, but if no network request actually started, it is possible that
+    // we only receive a status change with an error status code.
+    if (!Components.isSuccessCode(aStatus)) {
+      this._componentFailed = true;
+
+      // Wait for the associated Download object to be available.
+      this._deferDownload.promise.then(function DLT_OSC_onDownload(aDownload) {
+        aDownload.saver.onTransferFinished(aRequest, aStatus);
+      }).then(null, Cu.reportError);
+    }
+  },
+
+  onSecurityChange: function () { },
+
+  // nsIWebProgressListener2
+
+  onProgressChange64: function DLT_onProgressChange64(aWebProgress, aRequest,
+                                                      aCurSelfProgress,
+                                                      aMaxSelfProgress,
+                                                      aCurTotalProgress,
+                                                      aMaxTotalProgress)
+  {
+    // Wait for the associated Download object to be available.
+    this._deferDownload.promise.then(function DLT_OPC64_onDownload(aDownload) {
+      aDownload.saver.onProgressBytes(aCurTotalProgress, aMaxTotalProgress);
+    }).then(null, Cu.reportError);
+  },
+
+  onRefreshAttempted: function DLT_onRefreshAttempted(aWebProgress, aRefreshURI,
+                                                      aMillis, aSameURI)
+  {
+    // Indicate that refreshes and redirects are allowed by default.  However,
+    // note that download components don't usually call this method at all.
+    return true;
+  },
+
+  // nsITransfer
+
+  init: function DLT_init(aSource, aTarget, aDisplayName, aMIMEInfo, aStartTime,
+                          aTempFile, aCancelable, aIsPrivate)
+  {
+    this._cancelable = aCancelable;
+
+    let launchWhenSucceeded = false, contentType = null, launcherPath = null;
+
+    if (aMIMEInfo instanceof Ci.nsIMIMEInfo) {
+      launchWhenSucceeded =
+                aMIMEInfo.preferredAction != Ci.nsIMIMEInfo.saveToDisk;
+      contentType = aMIMEInfo.type;
+
+      let appHandler = aMIMEInfo.preferredApplicationHandler;
+      if (aMIMEInfo.preferredAction == Ci.nsIMIMEInfo.useHelperApp &&
+          appHandler instanceof Ci.nsILocalHandlerApp) {
+        launcherPath = appHandler.executable.path;
+      }
+    }
+
+    // Create a new Download object associated to a DownloadLegacySaver, and
+    // wait for it to be available.  This operation may cause the entire
+    // download system to initialize before the object is created.
+    Downloads.createDownload({
+      source: { url: aSource.spec, isPrivate: aIsPrivate },
+      target: { path: aTarget.QueryInterface(Ci.nsIFileURL).file.path,
+                partFilePath: aTempFile && aTempFile.path },
+      saver: "legacy",
+      launchWhenSucceeded: launchWhenSucceeded,
+      contentType: contentType,
+      launcherPath: launcherPath
+    }).then(function DLT_I_onDownload(aDownload) {
+      // Legacy components keep partial data when they use a ".part" file.
+      if (aTempFile) {
+        aDownload.tryToKeepPartialData = true;
+      }
+
+      // Start the download before allowing it to be controlled.  Ignore errors.
+      aDownload.start().catch(() => {});
+
+      // Start processing all the other events received through nsITransfer.
+      this._deferDownload.resolve(aDownload);
+
+      // Add the download to the list, allowing it to be seen and canceled.
+      return Downloads.getList(Downloads.ALL).then(list => list.add(aDownload));
+    }.bind(this)).then(null, Cu.reportError);
+  },
+
+  setSha256Hash: function (hash)
+  {
+    this._sha256Hash = hash;
+  },
+
+  setSignatureInfo: function (signatureInfo)
+  {
+    this._signatureInfo = signatureInfo;
+  },
+
+  setRedirects: function (redirects)
+  {
+    this._redirects = redirects;
+  },
+
+  // Private methods and properties
+
+  /**
+   * This deferred object contains a promise that is resolved with the Download
+   * object associated with this nsITransfer instance, when it is available.
+   */
+  _deferDownload: null,
+
+  /**
+   * Reference to the component that is executing the download.  This component
+   * allows cancellation through its nsICancelable interface.
+   */
+  _cancelable: null,
+
+  /**
+   * Indicates that the component that executes the download has notified a
+   * failure condition.  In this case, we should never use the component methods
+   * that cancel the download.
+   */
+  _componentFailed: false,
+
+  /**
+   * Save the SHA-256 hash in raw bytes of the downloaded file.
+   */
+  _sha256Hash: null,
+
+  /**
+   * Save the signature info in a serialized protobuf of the downloaded file.
+   */
+  _signatureInfo: null,
+};
+
+// Module
+
+this.NSGetFactory = XPCOMUtils.generateNSGetFactory([DownloadLegacyTransfer]);
diff --git a/toolkit/components/jsdownloads/src/DownloadList.jsm b/toolkit/components/jsdownloads/src/DownloadList.jsm
new file mode 100644
index 000000000..f725bd3de
--- /dev/null
+++ b/toolkit/components/jsdownloads/src/DownloadList.jsm
@@ -0,0 +1,559 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* 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/. */
+
+/**
+ * This file includes the following constructors and global objects:
+ *
+ * DownloadList
+ * Represents a collection of Download objects that can be viewed and managed by
+ * the user interface, and persisted across sessions.
+ *
+ * DownloadCombinedList
+ * Provides a unified, unordered list combining public and private downloads.
+ *
+ * DownloadSummary
+ * Provides an aggregated view on the contents of a DownloadList.
+ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "DownloadList",
+  "DownloadCombinedList",
+  "DownloadSummary",
+];
+
+// Globals
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+const Cr = Components.results;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "Promise",
+                                  "resource://gre/modules/Promise.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+                                  "resource://gre/modules/Task.jsm");
+
+// DownloadList
+
+/**
+ * Represents a collection of Download objects that can be viewed and managed by
+ * the user interface, and persisted across sessions.
+ */
+this.DownloadList = function ()
+{
+  this._downloads = [];
+  this._views = new Set();
+}
+
+this.DownloadList.prototype = {
+  /**
+   * Array of Download objects currently in the list.
+   */
+  _downloads: null,
+
+  /**
+   * Retrieves a snapshot of the downloads that are currently in the list.  The
+   * returned array does not change when downloads are added or removed, though
+   * the Download objects it contains are still updated in real time.
+   *
+   * @return {Promise}
+   * @resolves An array of Download objects.
+   * @rejects JavaScript exception.
+   */
+  getAll: function DL_getAll() {
+    return Promise.resolve(Array.slice(this._downloads, 0));
+  },
+
+  /**
+   * Adds a new download to the end of the items list.
+   *
+   * @note When a download is added to the list, its "onchange" event is
+   *       registered by the list, thus it cannot be used to monitor the
+   *       download.  To receive change notifications for downloads that are
+   *       added to the list, use the addView method to register for
+   *       onDownloadChanged notifications.
+   *
+   * @param aDownload
+   *        The Download object to add.
+   *
+   * @return {Promise}
+   * @resolves When the download has been added.
+   * @rejects JavaScript exception.
+   */
+  add: function DL_add(aDownload) {
+    this._downloads.push(aDownload);
+    aDownload.onchange = this._change.bind(this, aDownload);
+    this._notifyAllViews("onDownloadAdded", aDownload);
+
+    return Promise.resolve();
+  },
+
+  /**
+   * Removes a download from the list.  If the download was already removed,
+   * this method has no effect.
+   *
+   * This method does not change the state of the download, to allow adding it
+   * to another list, or control it directly.  If you want to dispose of the
+   * download object, you should cancel it afterwards, and remove any partially
+   * downloaded data if needed.
+   *
+   * @param aDownload
+   *        The Download object to remove.
+   *
+   * @return {Promise}
+   * @resolves When the download has been removed.
+   * @rejects JavaScript exception.
+   */
+  remove: function DL_remove(aDownload) {
+    let index = this._downloads.indexOf(aDownload);
+    if (index != -1) {
+      this._downloads.splice(index, 1);
+      aDownload.onchange = null;
+      this._notifyAllViews("onDownloadRemoved", aDownload);
+    }
+
+    return Promise.resolve();
+  },
+
+  /**
+   * This function is called when "onchange" events of downloads occur.
+   *
+   * @param aDownload
+   *        The Download object that changed.
+   */
+  _change: function DL_change(aDownload) {
+    this._notifyAllViews("onDownloadChanged", aDownload);
+  },
+
+  /**
+   * Set of currently registered views.
+   */
+  _views: null,
+
+  /**
+   * Adds a view that will be notified of changes to downloads.  The newly added
+   * view will receive onDownloadAdded notifications for all the downloads that
+   * are already in the list.
+   *
+   * @param aView
+   *        The view object to add.  The following methods may be defined:
+   *        {
+   *          onDownloadAdded: function (aDownload) {
+   *            // Called after aDownload is added to the end of the list.
+   *          },
+   *          onDownloadChanged: function (aDownload) {
+   *            // Called after the properties of aDownload change.
+   *          },
+   *          onDownloadRemoved: function (aDownload) {
+   *            // Called after aDownload is removed from the list.
+   *          },
+   *        }
+   *
+   * @return {Promise}
+   * @resolves When the view has been registered and all the onDownloadAdded
+   *           notifications for the existing downloads have been sent.
+   * @rejects JavaScript exception.
+   */
+  addView: function DL_addView(aView)
+  {
+    this._views.add(aView);
+
+    if ("onDownloadAdded" in aView) {
+      for (let download of this._downloads) {
+        try {
+          aView.onDownloadAdded(download);
+        } catch (ex) {
+          Cu.reportError(ex);
+        }
+      }
+    }
+
+    return Promise.resolve();
+  },
+
+  /**
+   * Removes a view that was previously added using addView.
+   *
+   * @param aView
+   *        The view object to remove.
+   *
+   * @return {Promise}
+   * @resolves When the view has been removed.  At this point, the removed view
+   *           will not receive any more notifications.
+   * @rejects JavaScript exception.
+   */
+  removeView: function DL_removeView(aView)
+  {
+    this._views.delete(aView);
+
+    return Promise.resolve();
+  },
+
+  /**
+   * Notifies all the views of a download addition, change, or removal.
+   *
+   * @param aMethodName
+   *        String containing the name of the method to call on the view.
+   * @param aDownload
+   *        The Download object that changed.
+   */
+  _notifyAllViews: function (aMethodName, aDownload) {
+    for (let view of this._views) {
+      try {
+        if (aMethodName in view) {
+          view[aMethodName](aDownload);
+        }
+      } catch (ex) {
+        Cu.reportError(ex);
+      }
+    }
+  },
+
+  /**
+   * Removes downloads from the list that have finished, have failed, or have
+   * been canceled without keeping partial data.  A filter function may be
+   * specified to remove only a subset of those downloads.
+   *
+   * This method finalizes each removed download, ensuring that any partially
+   * downloaded data associated with it is also removed.
+   *
+   * @param aFilterFn
+   *        The filter function is called with each download as its only
+   *        argument, and should return true to remove the download and false
+   *        to keep it.  This parameter may be null or omitted to have no
+   *        additional filter.
+   */
+  removeFinished: function DL_removeFinished(aFilterFn) {
+    Task.spawn(function* () {
+      let list = yield this.getAll();
+      for (let download of list) {
+        // Remove downloads that have been canceled, even if the cancellation
+        // operation hasn't completed yet so we don't check "stopped" here.
+        // Failed downloads with partial data are also removed.
+        if (download.stopped && (!download.hasPartialData || download.error) &&
+            (!aFilterFn || aFilterFn(download))) {
+          // Remove the download first, so that the views don't get the change
+          // notifications that may occur during finalization.
+          yield this.remove(download);
+          // Ensure that the download is stopped and no partial data is kept.
+          // This works even if the download state has changed meanwhile.  We
+          // don't need to wait for the procedure to be complete before
+          // processing the other downloads in the list.
+          download.finalize(true).then(null, Cu.reportError);
+        }
+      }
+    }.bind(this)).then(null, Cu.reportError);
+  },
+};
+
+// DownloadCombinedList
+
+/**
+ * Provides a unified, unordered list combining public and private downloads.
+ *
+ * Download objects added to this list are also added to one of the two
+ * underlying lists, based on their "source.isPrivate" property.  Views on this
+ * list will receive notifications for both public and private downloads.
+ *
+ * @param aPublicList
+ *        Underlying DownloadList containing public downloads.
+ * @param aPrivateList
+ *        Underlying DownloadList containing private downloads.
+ */
+this.DownloadCombinedList = function (aPublicList, aPrivateList)
+{
+  DownloadList.call(this);
+  this._publicList = aPublicList;
+  this._privateList = aPrivateList;
+  aPublicList.addView(this).then(null, Cu.reportError);
+  aPrivateList.addView(this).then(null, Cu.reportError);
+}
+
+this.DownloadCombinedList.prototype = {
+  __proto__: DownloadList.prototype,
+
+  /**
+   * Underlying DownloadList containing public downloads.
+   */
+  _publicList: null,
+
+  /**
+   * Underlying DownloadList containing private downloads.
+   */
+  _privateList: null,
+
+  /**
+   * Adds a new download to the end of the items list.
+   *
+   * @note When a download is added to the list, its "onchange" event is
+   *       registered by the list, thus it cannot be used to monitor the
+   *       download.  To receive change notifications for downloads that are
+   *       added to the list, use the addView method to register for
+   *       onDownloadChanged notifications.
+   *
+   * @param aDownload
+   *        The Download object to add.
+   *
+   * @return {Promise}
+   * @resolves When the download has been added.
+   * @rejects JavaScript exception.
+   */
+  add: function (aDownload)
+  {
+    if (aDownload.source.isPrivate) {
+      return this._privateList.add(aDownload);
+    }
+    return this._publicList.add(aDownload);
+  },
+
+  /**
+   * Removes a download from the list.  If the download was already removed,
+   * this method has no effect.
+   *
+   * This method does not change the state of the download, to allow adding it
+   * to another list, or control it directly.  If you want to dispose of the
+   * download object, you should cancel it afterwards, and remove any partially
+   * downloaded data if needed.
+   *
+   * @param aDownload
+   *        The Download object to remove.
+   *
+   * @return {Promise}
+   * @resolves When the download has been removed.
+   * @rejects JavaScript exception.
+   */
+  remove: function (aDownload)
+  {
+    if (aDownload.source.isPrivate) {
+      return this._privateList.remove(aDownload);
+    }
+    return this._publicList.remove(aDownload);
+  },
+
+  // DownloadList view
+
+  onDownloadAdded: function (aDownload)
+  {
+    this._downloads.push(aDownload);
+    this._notifyAllViews("onDownloadAdded", aDownload);
+  },
+
+  onDownloadChanged: function (aDownload)
+  {
+    this._notifyAllViews("onDownloadChanged", aDownload);
+  },
+
+  onDownloadRemoved: function (aDownload)
+  {
+    let index = this._downloads.indexOf(aDownload);
+    if (index != -1) {
+      this._downloads.splice(index, 1);
+    }
+    this._notifyAllViews("onDownloadRemoved", aDownload);
+  },
+};
+
+// DownloadSummary
+
+/**
+ * Provides an aggregated view on the contents of a DownloadList.
+ */
+this.DownloadSummary = function ()
+{
+  this._downloads = [];
+  this._views = new Set();
+}
+
+this.DownloadSummary.prototype = {
+  /**
+   * Array of Download objects that are currently part of the summary.
+   */
+  _downloads: null,
+
+  /**
+   * Underlying DownloadList whose contents should be summarized.
+   */
+  _list: null,
+
+  /**
+   * This method may be called once to bind this object to a DownloadList.
+   *
+   * Views on the summarized data can be registered before this object is bound
+   * to an actual list.  This allows the summary to be used without requiring
+   * the initialization of the DownloadList first.
+   *
+   * @param aList
+   *        Underlying DownloadList whose contents should be summarized.
+   *
+   * @return {Promise}
+   * @resolves When the view on the underlying list has been registered.
+   * @rejects JavaScript exception.
+   */
+  bindToList: function (aList)
+  {
+    if (this._list) {
+      throw new Error("bindToList may be called only once.");
+    }
+
+    return aList.addView(this).then(() => {
+      // Set the list reference only after addView has returned, so that we don't
+      // send a notification to our views for each download that is added.
+      this._list = aList;
+      this._onListChanged();
+    });
+  },
+
+  /**
+   * Set of currently registered views.
+   */
+  _views: null,
+
+  /**
+   * Adds a view that will be notified of changes to the summary.  The newly
+   * added view will receive an initial onSummaryChanged notification.
+   *
+   * @param aView
+   *        The view object to add.  The following methods may be defined:
+   *        {
+   *          onSummaryChanged: function () {
+   *            // Called after any property of the summary has changed.
+   *          },
+   *        }
+   *
+   * @return {Promise}
+   * @resolves When the view has been registered and the onSummaryChanged
+   *           notification has been sent.
+   * @rejects JavaScript exception.
+   */
+  addView: function (aView)
+  {
+    this._views.add(aView);
+
+    if ("onSummaryChanged" in aView) {
+      try {
+        aView.onSummaryChanged();
+      } catch (ex) {
+        Cu.reportError(ex);
+      }
+    }
+
+    return Promise.resolve();
+  },
+
+  /**
+   * Removes a view that was previously added using addView.
+   *
+   * @param aView
+   *        The view object to remove.
+   *
+   * @return {Promise}
+   * @resolves When the view has been removed.  At this point, the removed view
+   *           will not receive any more notifications.
+   * @rejects JavaScript exception.
+   */
+  removeView: function (aView)
+  {
+    this._views.delete(aView);
+
+    return Promise.resolve();
+  },
+
+  /**
+   * Indicates whether all the downloads are currently stopped.
+   */
+  allHaveStopped: true,
+
+  /**
+   * Indicates the total number of bytes to be transferred before completing all
+   * the downloads that are currently in progress.
+   *
+   * For downloads that do not have a known final size, the number of bytes
+   * currently transferred is reported as part of this property.
+   *
+   * This is zero if no downloads are currently in progress.
+   */
+  progressTotalBytes: 0,
+
+  /**
+   * Number of bytes currently transferred as part of all the downloads that are
+   * currently in progress.
+   *
+   * This is zero if no downloads are currently in progress.
+   */
+  progressCurrentBytes: 0,
+
+  /**
+   * This function is called when any change in the list of downloads occurs,
+   * and will recalculate the summary and notify the views in case the
+   * aggregated properties are different.
+   */
+  _onListChanged: function () {
+    let allHaveStopped = true;
+    let progressTotalBytes = 0;
+    let progressCurrentBytes = 0;
+
+    // Recalculate the aggregated state.  See the description of the individual
+    // properties for an explanation of the summarization logic.
+    for (let download of this._downloads) {
+      if (!download.stopped) {
+        allHaveStopped = false;
+        progressTotalBytes += download.hasProgress ? download.totalBytes
+                                                   : download.currentBytes;
+        progressCurrentBytes += download.currentBytes;
+      }
+    }
+
+    // Exit now if the properties did not change.
+    if (this.allHaveStopped == allHaveStopped &&
+        this.progressTotalBytes == progressTotalBytes &&
+        this.progressCurrentBytes == progressCurrentBytes) {
+      return;
+    }
+
+    this.allHaveStopped = allHaveStopped;
+    this.progressTotalBytes = progressTotalBytes;
+    this.progressCurrentBytes = progressCurrentBytes;
+
+    // Notify all the views that our properties changed.
+    for (let view of this._views) {
+      try {
+        if ("onSummaryChanged" in view) {
+          view.onSummaryChanged();
+        }
+      } catch (ex) {
+        Cu.reportError(ex);
+      }
+    }
+  },
+
+  // DownloadList view
+
+  onDownloadAdded: function (aDownload)
+  {
+    this._downloads.push(aDownload);
+    if (this._list) {
+      this._onListChanged();
+    }
+  },
+
+  onDownloadChanged: function (aDownload)
+  {
+    this._onListChanged();
+  },
+
+  onDownloadRemoved: function (aDownload)
+  {
+    let index = this._downloads.indexOf(aDownload);
+    if (index != -1) {
+      this._downloads.splice(index, 1);
+    }
+    this._onListChanged();
+  },
+};
diff --git a/toolkit/components/jsdownloads/src/DownloadPlatform.cpp b/toolkit/components/jsdownloads/src/DownloadPlatform.cpp
new file mode 100644
index 000000000..1506b7c30
--- /dev/null
+++ b/toolkit/components/jsdownloads/src/DownloadPlatform.cpp
@@ -0,0 +1,275 @@
+/* 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/. */
+
+#include "DownloadPlatform.h"
+#include "nsAutoPtr.h"
+#include "nsNetUtil.h"
+#include "nsString.h"
+#include "nsINestedURI.h"
+#include "nsIProtocolHandler.h"
+#include "nsIURI.h"
+#include "nsIFile.h"
+#include "nsIObserverService.h"
+#include "nsISupportsPrimitives.h"
+#include "nsDirectoryServiceDefs.h"
+
+#include "mozilla/Preferences.h"
+#include "mozilla/Services.h"
+
+#define PREF_BDM_ADDTORECENTDOCS "browser.download.manager.addToRecentDocs"
+
+#ifdef XP_WIN
+#include <shlobj.h>
+#include <urlmon.h>
+#include "nsILocalFileWin.h"
+#endif
+
+#ifdef XP_MACOSX
+#include <CoreFoundation/CoreFoundation.h>
+#include "../../../../xpcom/io/CocoaFileUtils.h"
+#endif
+
+#ifdef MOZ_WIDGET_ANDROID
+#include "FennecJNIWrappers.h"
+#endif
+
+#ifdef MOZ_WIDGET_GTK
+#include <gtk/gtk.h>
+#endif
+
+using namespace mozilla;
+
+DownloadPlatform *DownloadPlatform::gDownloadPlatformService = nullptr;
+
+NS_IMPL_ISUPPORTS(DownloadPlatform, mozIDownloadPlatform);
+
+DownloadPlatform* DownloadPlatform::GetDownloadPlatform()
+{
+  if (!gDownloadPlatformService) {
+    gDownloadPlatformService = new DownloadPlatform();
+  }
+
+  NS_ADDREF(gDownloadPlatformService);
+
+#if defined(MOZ_WIDGET_GTK)
+  g_type_init();
+#endif
+
+  return gDownloadPlatformService;
+}
+
+#ifdef MOZ_ENABLE_GIO
+static void gio_set_metadata_done(GObject *source_obj, GAsyncResult *res, gpointer user_data)
+{
+  GError *err = nullptr;
+  g_file_set_attributes_finish(G_FILE(source_obj), res, nullptr, &err);
+  if (err) {
+#ifdef DEBUG
+    NS_DebugBreak(NS_DEBUG_WARNING, "Set file metadata failed: ", err->message, __FILE__, __LINE__);
+#endif
+    g_error_free(err);
+  }
+}
+#endif
+
+#ifdef XP_MACOSX
+// Caller is responsible for freeing any result (CF Create Rule)
+CFURLRef CreateCFURLFromNSIURI(nsIURI *aURI) {
+  nsAutoCString spec;
+  if (aURI) {
+    aURI->GetSpec(spec);
+  }
+
+  CFStringRef urlStr = ::CFStringCreateWithCString(kCFAllocatorDefault,
+                                                   spec.get(),
+                                                   kCFStringEncodingUTF8);
+  if (!urlStr) {
+    return NULL;
+  }
+
+  CFURLRef url = ::CFURLCreateWithString(kCFAllocatorDefault,
+                                         urlStr,
+                                         NULL);
+
+  ::CFRelease(urlStr);
+
+  return url;
+}
+#endif
+
+nsresult DownloadPlatform::DownloadDone(nsIURI* aSource, nsIURI* aReferrer, nsIFile* aTarget,
+                                        const nsACString& aContentType, bool aIsPrivate)
+{
+#if defined(XP_WIN) || defined(XP_MACOSX) || defined(MOZ_WIDGET_ANDROID) \
+ || defined(MOZ_WIDGET_GTK) || defined(MOZ_WIDGET_GONK)
+
+  nsAutoString path;
+  if (aTarget && NS_SUCCEEDED(aTarget->GetPath(path))) {
+#if defined(XP_WIN) || defined(MOZ_WIDGET_GTK) || defined(MOZ_WIDGET_ANDROID)
+    // On Windows and Gtk, add the download to the system's "recent documents"
+    // list, with a pref to disable.
+    {
+      bool addToRecentDocs = Preferences::GetBool(PREF_BDM_ADDTORECENTDOCS);
+#ifdef MOZ_WIDGET_ANDROID
+      if (jni::IsFennec() && addToRecentDocs) {
+        java::DownloadsIntegration::ScanMedia(path, aContentType);
+      }
+#else
+      if (addToRecentDocs && !aIsPrivate) {
+#ifdef XP_WIN
+        ::SHAddToRecentDocs(SHARD_PATHW, path.get());
+#elif defined(MOZ_WIDGET_GTK)
+        GtkRecentManager* manager = gtk_recent_manager_get_default();
+
+        gchar* uri = g_filename_to_uri(NS_ConvertUTF16toUTF8(path).get(),
+                                       nullptr, nullptr);
+        if (uri) {
+          gtk_recent_manager_add_item(manager, uri);
+          g_free(uri);
+        }
+#endif
+      }
+#endif
+#ifdef MOZ_ENABLE_GIO
+      // Use GIO to store the source URI for later display in the file manager.
+      GFile* gio_file = g_file_new_for_path(NS_ConvertUTF16toUTF8(path).get());
+      nsCString source_uri;
+      nsresult rv = aSource->GetSpec(source_uri);
+      NS_ENSURE_SUCCESS(rv, rv);
+      GFileInfo *file_info = g_file_info_new();
+      g_file_info_set_attribute_string(file_info, "metadata::download-uri", source_uri.get());
+      g_file_set_attributes_async(gio_file,
+                                  file_info,
+                                  G_FILE_QUERY_INFO_NONE,
+                                  G_PRIORITY_DEFAULT,
+                                  nullptr, gio_set_metadata_done, nullptr);
+      g_object_unref(file_info);
+      g_object_unref(gio_file);
+#endif
+    }
+#endif
+
+#ifdef XP_MACOSX
+    // On OS X, make the downloads stack bounce.
+    CFStringRef observedObject = ::CFStringCreateWithCString(kCFAllocatorDefault,
+                                             NS_ConvertUTF16toUTF8(path).get(),
+                                             kCFStringEncodingUTF8);
+    CFNotificationCenterRef center = ::CFNotificationCenterGetDistributedCenter();
+    ::CFNotificationCenterPostNotification(center, CFSTR("com.apple.DownloadFileFinished"),
+                                           observedObject, nullptr, TRUE);
+    ::CFRelease(observedObject);
+
+    // Add OS X origin and referrer file metadata
+    CFStringRef pathCFStr = NULL;
+    if (!path.IsEmpty()) {
+      pathCFStr = ::CFStringCreateWithCharacters(kCFAllocatorDefault,
+                                                 (const UniChar*)path.get(),
+                                                 path.Length());
+    }
+    if (pathCFStr) {
+      bool isFromWeb = IsURLPossiblyFromWeb(aSource);
+
+      CFURLRef sourceCFURL = CreateCFURLFromNSIURI(aSource);
+      CFURLRef referrerCFURL = CreateCFURLFromNSIURI(aReferrer);
+
+      CocoaFileUtils::AddOriginMetadataToFile(pathCFStr,
+                                              sourceCFURL,
+                                              referrerCFURL);
+      CocoaFileUtils::AddQuarantineMetadataToFile(pathCFStr,
+                                                  sourceCFURL,
+                                                  referrerCFURL,
+                                                  isFromWeb);
+
+      ::CFRelease(pathCFStr);
+      if (sourceCFURL) {
+        ::CFRelease(sourceCFURL);
+      }
+      if (referrerCFURL) {
+        ::CFRelease(referrerCFURL);
+      }
+    }
+#endif
+  }
+
+#endif
+
+  return NS_OK;
+}
+
+nsresult DownloadPlatform::MapUrlToZone(const nsAString& aURL,
+                                        uint32_t* aZone)
+{
+#ifdef XP_WIN
+  RefPtr<IInternetSecurityManager> inetSecMgr;
+  if (FAILED(CoCreateInstance(CLSID_InternetSecurityManager, NULL,
+                              CLSCTX_ALL, IID_IInternetSecurityManager,
+                              getter_AddRefs(inetSecMgr)))) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  DWORD zone;
+  if (inetSecMgr->MapUrlToZone(PromiseFlatString(aURL).get(),
+                               &zone, 0) != S_OK) {
+    return NS_ERROR_UNEXPECTED;
+  } else {
+    *aZone = zone;
+  }
+
+  return NS_OK;
+#else
+  return NS_ERROR_NOT_IMPLEMENTED;
+#endif
+}
+
+// Check if a URI is likely to be web-based, by checking its URI flags.
+// If in doubt (e.g. if anything fails during the check) claims things
+// are from the web.
+bool DownloadPlatform::IsURLPossiblyFromWeb(nsIURI* aURI)
+{
+  nsCOMPtr<nsIIOService> ios = do_GetIOService();
+  nsCOMPtr<nsIURI> uri = aURI;
+  if (!ios) {
+    return true;
+  }
+
+  while (uri) {
+    // We're not using nsIIOService::ProtocolHasFlags because it doesn't
+    // take per-URI flags into account. We're also not using
+    // NS_URIChainHasFlags because we're checking for *any* of 3 flags
+    // to be present on *all* of the nested URIs, which it can't do.
+    nsAutoCString scheme;
+    nsresult rv = uri->GetScheme(scheme);
+    if (NS_FAILED(rv)) {
+      return true;
+    }
+    nsCOMPtr<nsIProtocolHandler> ph;
+    rv = ios->GetProtocolHandler(scheme.get(), getter_AddRefs(ph));
+    if (NS_FAILED(rv)) {
+      return true;
+    }
+    uint32_t flags;
+    rv = ph->DoGetProtocolFlags(uri, &flags);
+    if (NS_FAILED(rv)) {
+      return true;
+    }
+    // If not dangerous to load, not a UI resource and not a local file,
+    // assume this is from the web:
+    if (!(flags & nsIProtocolHandler::URI_DANGEROUS_TO_LOAD) &&
+        !(flags & nsIProtocolHandler::URI_IS_UI_RESOURCE) &&
+        !(flags & nsIProtocolHandler::URI_IS_LOCAL_FILE)) {
+      return true;
+    }
+    // Otherwise, check if the URI is nested, and if so go through
+    // the loop again:
+    nsCOMPtr<nsINestedURI> nestedURI = do_QueryInterface(uri);
+    uri = nullptr;
+    if (nestedURI) {
+      rv = nestedURI->GetInnerURI(getter_AddRefs(uri));
+      if (NS_FAILED(rv)) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
diff --git a/toolkit/components/jsdownloads/src/DownloadPlatform.h b/toolkit/components/jsdownloads/src/DownloadPlatform.h
new file mode 100644
index 000000000..ef3c7554f
--- /dev/null
+++ b/toolkit/components/jsdownloads/src/DownloadPlatform.h
@@ -0,0 +1,34 @@
+/* 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/. */
+
+#ifndef __DownloadPlatform_h__
+#define __DownloadPlatform_h__
+
+#include "mozIDownloadPlatform.h"
+
+#include "nsCOMPtr.h"
+class nsIURI;
+
+class DownloadPlatform : public mozIDownloadPlatform
+{
+protected:
+
+  virtual ~DownloadPlatform() { }
+
+public:
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_MOZIDOWNLOADPLATFORM
+
+  DownloadPlatform() { }
+
+  static DownloadPlatform *gDownloadPlatformService;
+
+  static DownloadPlatform* GetDownloadPlatform();
+
+private:
+  static bool IsURLPossiblyFromWeb(nsIURI* aURI);
+};
+
+#endif
diff --git a/toolkit/components/jsdownloads/src/DownloadStore.jsm b/toolkit/components/jsdownloads/src/DownloadStore.jsm
new file mode 100644
index 000000000..765a45c5a
--- /dev/null
+++ b/toolkit/components/jsdownloads/src/DownloadStore.jsm
@@ -0,0 +1,203 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* 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/. */
+
+/**
+ * Handles serialization of Download objects and persistence into a file, so
+ * that the state of downloads can be restored across sessions.
+ *
+ * The file is stored in JSON format, without indentation.  With indentation
+ * applied, the file would look like this:
+ *
+ * {
+ *   "list": [
+ *     {
+ *       "source": "http://www.example.com/download.txt",
+ *       "target": "/home/user/Downloads/download.txt"
+ *     },
+ *     {
+ *       "source": {
+ *         "url": "http://www.example.com/download.txt",
+ *         "referrer": "http://www.example.com/referrer.html"
+ *       },
+ *       "target": "/home/user/Downloads/download-2.txt"
+ *     }
+ *   ]
+ * }
+ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "DownloadStore",
+];
+
+// Globals
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+const Cr = Components.results;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "Downloads",
+                                  "resource://gre/modules/Downloads.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "OS",
+                                  "resource://gre/modules/osfile.jsm")
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+                                  "resource://gre/modules/Task.jsm");
+
+XPCOMUtils.defineLazyGetter(this, "gTextDecoder", function () {
+  return new TextDecoder();
+});
+
+XPCOMUtils.defineLazyGetter(this, "gTextEncoder", function () {
+  return new TextEncoder();
+});
+
+// DownloadStore
+
+/**
+ * Handles serialization of Download objects and persistence into a file, so
+ * that the state of downloads can be restored across sessions.
+ *
+ * @param aList
+ *        DownloadList object to be populated or serialized.
+ * @param aPath
+ *        String containing the file path where data should be saved.
+ */
+this.DownloadStore = function (aList, aPath)
+{
+  this.list = aList;
+  this.path = aPath;
+}
+
+this.DownloadStore.prototype = {
+  /**
+   * DownloadList object to be populated or serialized.
+   */
+  list: null,
+
+  /**
+   * String containing the file path where data should be saved.
+   */
+  path: "",
+
+  /**
+   * This function is called with a Download object as its first argument, and
+   * should return true if the item should be saved.
+   */
+  onsaveitem: () => true,
+
+  /**
+   * Loads persistent downloads from the file to the list.
+   *
+   * @return {Promise}
+   * @resolves When the operation finished successfully.
+   * @rejects JavaScript exception.
+   */
+  load: function DS_load()
+  {
+    return Task.spawn(function* task_DS_load() {
+      let bytes;
+      try {
+        bytes = yield OS.File.read(this.path);
+      } catch (ex) {
+        if (!(ex instanceof OS.File.Error) || !ex.becauseNoSuchFile) {
+          throw ex;
+        }
+        // If the file does not exist, there are no downloads to load.
+        return;
+      }
+
+      let storeData = JSON.parse(gTextDecoder.decode(bytes));
+
+      // Create live downloads based on the static snapshot.
+      for (let downloadData of storeData.list) {
+        try {
+          let download = yield Downloads.createDownload(downloadData);
+          try {
+            if (!download.succeeded && !download.canceled && !download.error) {
+              // Try to restart the download if it was in progress during the
+              // previous session.  Ignore errors.
+              download.start().catch(() => {});
+            } else {
+              // If the download was not in progress, try to update the current
+              // progress from disk.  This is relevant in case we retained
+              // partially downloaded data.
+              yield download.refresh();
+            }
+          } finally {
+            // Add the download to the list if we succeeded in creating it,
+            // after we have updated its initial state.
+            yield this.list.add(download);
+          }
+        } catch (ex) {
+          // If an item is unrecognized, don't prevent others from being loaded.
+          Cu.reportError(ex);
+        }
+      }
+    }.bind(this));
+  },
+
+  /**
+   * Saves persistent downloads from the list to the file.
+   *
+   * If an error occurs, the previous file is not deleted.
+   *
+   * @return {Promise}
+   * @resolves When the operation finished successfully.
+   * @rejects JavaScript exception.
+   */
+  save: function DS_save()
+  {
+    return Task.spawn(function* task_DS_save() {
+      let downloads = yield this.list.getAll();
+
+      // Take a static snapshot of the current state of all the downloads.
+      let storeData = { list: [] };
+      let atLeastOneDownload = false;
+      for (let download of downloads) {
+        try {
+          if (!this.onsaveitem(download)) {
+            continue;
+          }
+
+          let serializable = download.toSerializable();
+          if (!serializable) {
+            // This item cannot be persisted across sessions.
+            continue;
+          }
+          storeData.list.push(serializable);
+          atLeastOneDownload = true;
+        } catch (ex) {
+          // If an item cannot be converted to a serializable form, don't
+          // prevent others from being saved.
+          Cu.reportError(ex);
+        }
+      }
+
+      if (atLeastOneDownload) {
+        // Create or overwrite the file if there are downloads to save.
+        let bytes = gTextEncoder.encode(JSON.stringify(storeData));
+        yield OS.File.writeAtomic(this.path, bytes,
+                                  { tmpPath: this.path + ".tmp" });
+      } else {
+        // Remove the file if there are no downloads to save at all.
+        try {
+          yield OS.File.remove(this.path);
+        } catch (ex) {
+          if (!(ex instanceof OS.File.Error) ||
+              !(ex.becauseNoSuchFile || ex.becauseAccessDenied)) {
+            throw ex;
+          }
+          // On Windows, we may get an access denied error instead of a no such
+          // file error if the file existed before, and was recently deleted.
+        }
+      }
+    }.bind(this));
+  },
+};
diff --git a/toolkit/components/jsdownloads/src/DownloadUIHelper.jsm b/toolkit/components/jsdownloads/src/DownloadUIHelper.jsm
new file mode 100644
index 000000000..f5102b4a8
--- /dev/null
+++ b/toolkit/components/jsdownloads/src/DownloadUIHelper.jsm
@@ -0,0 +1,243 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* 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/. */
+
+/**
+ * Provides functions to handle status and messages in the user interface.
+ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "DownloadUIHelper",
+];
+
+// Globals
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+const Cr = Components.results;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/AppConstants.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "OS",
+                                  "resource://gre/modules/osfile.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Promise",
+                                  "resource://gre/modules/Promise.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Services",
+                                  "resource://gre/modules/Services.jsm");
+
+const kStringBundleUrl =
+  "chrome://mozapps/locale/downloads/downloads.properties";
+
+const kStringsRequiringFormatting = {
+  fileExecutableSecurityWarning: true,
+  cancelDownloadsOKTextMultiple: true,
+  quitCancelDownloadsAlertMsgMultiple: true,
+  quitCancelDownloadsAlertMsgMacMultiple: true,
+  offlineCancelDownloadsAlertMsgMultiple: true,
+  leavePrivateBrowsingWindowsCancelDownloadsAlertMsgMultiple2: true
+};
+
+// DownloadUIHelper
+
+/**
+ * Provides functions to handle status and messages in the user interface.
+ */
+this.DownloadUIHelper = {
+  /**
+   * Returns an object that can be used to display prompts related to downloads.
+   *
+   * The prompts may be either anchored to a specified window, or anchored to
+   * the most recently active window, for example if the prompt is displayed in
+   * response to global notifications that are not associated with any window.
+   *
+   * @param aParent
+   *        If specified, should reference the nsIDOMWindow to which the prompts
+   *        should be attached.  If omitted, the prompts will be attached to the
+   *        most recently active window.
+   *
+   * @return A DownloadPrompter object.
+   */
+  getPrompter: function (aParent)
+  {
+    return new DownloadPrompter(aParent || null);
+  },
+};
+
+/**
+ * Returns an object whose keys are the string names from the downloads string
+ * bundle, and whose values are either the translated strings or functions
+ * returning formatted strings.
+ */
+XPCOMUtils.defineLazyGetter(DownloadUIHelper, "strings", function () {
+  let strings = {};
+  let sb = Services.strings.createBundle(kStringBundleUrl);
+  let enumerator = sb.getSimpleEnumeration();
+  while (enumerator.hasMoreElements()) {
+    let string = enumerator.getNext().QueryInterface(Ci.nsIPropertyElement);
+    let stringName = string.key;
+    if (stringName in kStringsRequiringFormatting) {
+      strings[stringName] = function () {
+        // Convert "arguments" to a real array before calling into XPCOM.
+        return sb.formatStringFromName(stringName,
+                                       Array.slice(arguments, 0),
+                                       arguments.length);
+      };
+    } else {
+      strings[stringName] = string.value;
+    }
+  }
+  return strings;
+});
+
+// DownloadPrompter
+
+/**
+ * Allows displaying prompts related to downloads.
+ *
+ * @param aParent
+ *        The nsIDOMWindow to which prompts should be attached, or null to
+ *        attach prompts to the most recently active window.
+ */
+this.DownloadPrompter = function (aParent)
+{
+  if (AppConstants.MOZ_B2G) {
+    // On B2G there is no prompter implementation.
+    this._prompter = null;
+  } else {
+    this._prompter = Services.ww.getNewPrompter(aParent);
+  }
+}
+
+this.DownloadPrompter.prototype = {
+  /**
+   * Constants with the different type of prompts.
+   */
+  ON_QUIT: "prompt-on-quit",
+  ON_OFFLINE: "prompt-on-offline",
+  ON_LEAVE_PRIVATE_BROWSING: "prompt-on-leave-private-browsing",
+
+  /**
+   * nsIPrompt instance for displaying messages.
+   */
+  _prompter: null,
+
+  /**
+   * Displays a warning message box that informs that the specified file is
+   * executable, and asks whether the user wants to launch it.  The user is
+   * given the option of disabling future instances of this warning.
+   *
+   * @param aPath
+   *        String containing the full path to the file to be opened.
+   *
+   * @return {Promise}
+   * @resolves Boolean indicating whether the launch operation can continue.
+   * @rejects JavaScript exception.
+   */
+  confirmLaunchExecutable: function (aPath)
+  {
+    const kPrefAlertOnEXEOpen = "browser.download.manager.alertOnEXEOpen";
+
+    try {
+      // Always launch in case we have no prompter implementation.
+      if (!this._prompter) {
+        return Promise.resolve(true);
+      }
+
+      try {
+        if (!Services.prefs.getBoolPref(kPrefAlertOnEXEOpen)) {
+          return Promise.resolve(true);
+        }
+      } catch (ex) {
+        // If the preference does not exist, continue with the prompt.
+      }
+
+      let leafName = OS.Path.basename(aPath);
+
+      let s = DownloadUIHelper.strings;
+      let checkState = { value: false };
+      let shouldLaunch = this._prompter.confirmCheck(
+                           s.fileExecutableSecurityWarningTitle,
+                           s.fileExecutableSecurityWarning(leafName, leafName),
+                           s.fileExecutableSecurityWarningDontAsk,
+                           checkState);
+
+      if (shouldLaunch) {
+        Services.prefs.setBoolPref(kPrefAlertOnEXEOpen, !checkState.value);
+      }
+
+      return Promise.resolve(shouldLaunch);
+    } catch (ex) {
+      return Promise.reject(ex);
+    }
+  },
+
+  /**
+   * Displays a warning message box that informs that there are active
+   * downloads, and asks whether the user wants to cancel them or not.
+   *
+   * @param aDownloadsCount
+   *        The current downloads count.
+   * @param aPromptType
+   *        The type of prompt notification depending on the observer.
+   *
+   * @return False to cancel the downloads and continue, true to abort the
+   *         operation.
+   */
+  confirmCancelDownloads: function DP_confirmCancelDownload(aDownloadsCount,
+                                                            aPromptType)
+  {
+    // Always continue in case we have no prompter implementation, or if there
+    // are no active downloads.
+    if (!this._prompter || aDownloadsCount <= 0) {
+      return false;
+    }
+
+    let s = DownloadUIHelper.strings;
+    let buttonFlags = (Ci.nsIPrompt.BUTTON_TITLE_IS_STRING * Ci.nsIPrompt.BUTTON_POS_0) +
+                      (Ci.nsIPrompt.BUTTON_TITLE_IS_STRING * Ci.nsIPrompt.BUTTON_POS_1);
+    let okButton = aDownloadsCount > 1 ? s.cancelDownloadsOKTextMultiple(aDownloadsCount)
+                                       : s.cancelDownloadsOKText;
+    let title, message, cancelButton;
+
+    switch (aPromptType) {
+      case this.ON_QUIT:
+        title = s.quitCancelDownloadsAlertTitle;
+        if (AppConstants.platform != "macosx") {
+          message = aDownloadsCount > 1
+                    ? s.quitCancelDownloadsAlertMsgMultiple(aDownloadsCount)
+                    : s.quitCancelDownloadsAlertMsg;
+          cancelButton = s.dontQuitButtonWin;
+        } else {
+          message = aDownloadsCount > 1
+                    ? s.quitCancelDownloadsAlertMsgMacMultiple(aDownloadsCount)
+                    : s.quitCancelDownloadsAlertMsgMac;
+          cancelButton = s.dontQuitButtonMac;
+        }
+        break;
+      case this.ON_OFFLINE:
+        title = s.offlineCancelDownloadsAlertTitle;
+        message = aDownloadsCount > 1
+                  ? s.offlineCancelDownloadsAlertMsgMultiple(aDownloadsCount)
+                  : s.offlineCancelDownloadsAlertMsg;
+        cancelButton = s.dontGoOfflineButton;
+        break;
+      case this.ON_LEAVE_PRIVATE_BROWSING:
+        title = s.leavePrivateBrowsingCancelDownloadsAlertTitle;
+        message = aDownloadsCount > 1
+                  ? s.leavePrivateBrowsingWindowsCancelDownloadsAlertMsgMultiple2(aDownloadsCount)
+                  : s.leavePrivateBrowsingWindowsCancelDownloadsAlertMsg2;
+        cancelButton = s.dontLeavePrivateBrowsingButton2;
+        break;
+    }
+
+    let rv = this._prompter.confirmEx(title, message, buttonFlags, okButton,
+                                      cancelButton, null, null, {});
+    return (rv == 1);
+  }
+};
diff --git a/toolkit/components/jsdownloads/src/Downloads.jsm b/toolkit/components/jsdownloads/src/Downloads.jsm
new file mode 100644
index 000000000..9511dc4ca
--- /dev/null
+++ b/toolkit/components/jsdownloads/src/Downloads.jsm
@@ -0,0 +1,305 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* 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/. */
+
+/**
+ * Main entry point to get references to all the back-end objects.
+ */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = [
+  "Downloads",
+];
+
+// Globals
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+const Cr = Components.results;
+
+Cu.import("resource://gre/modules/Integration.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/DownloadCore.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadCombinedList",
+                                  "resource://gre/modules/DownloadList.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadList",
+                                  "resource://gre/modules/DownloadList.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadSummary",
+                                  "resource://gre/modules/DownloadList.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "DownloadUIHelper",
+                                  "resource://gre/modules/DownloadUIHelper.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Promise",
+                                  "resource://gre/modules/Promise.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+                                  "resource://gre/modules/Task.jsm");
+
+Integration.downloads.defineModuleGetter(this, "DownloadIntegration",
+            "resource://gre/modules/DownloadIntegration.jsm");
+
+// Downloads
+
+/**
+ * This object is exposed directly to the consumers of this JavaScript module,
+ * and provides the only entry point to get references to back-end objects.
+ */
+this.Downloads = {
+  /**
+   * Work on downloads that were not started from a private browsing window.
+   */
+  get PUBLIC() {
+    return "{Downloads.PUBLIC}";
+  },
+  /**
+   * Work on downloads that were started from a private browsing window.
+   */
+  get PRIVATE() {
+    return "{Downloads.PRIVATE}";
+  },
+  /**
+   * Work on both Downloads.PRIVATE and Downloads.PUBLIC downloads.
+   */
+  get ALL() {
+    return "{Downloads.ALL}";
+  },
+
+  /**
+   * Creates a new Download object.
+   *
+   * @param aProperties
+   *        Provides the initial properties for the newly created download.
+   *        This matches the serializable representation of a Download object.
+   *        Some of the most common properties in this object include:
+   *        {
+   *          source: String containing the URI for the download source.
+   *                  Alternatively, may be an nsIURI, a DownloadSource object,
+   *                  or an object with the following properties:
+   *          {
+   *            url: String containing the URI for the download source.
+   *            isPrivate: Indicates whether the download originated from a
+   *                       private window.  If omitted, the download is public.
+   *            referrer: String containing the referrer URI of the download
+   *                      source.  Can be omitted or null if no referrer should
+   *                      be sent or the download source is not HTTP.
+   *          },
+   *          target: String containing the path of the target file.
+   *                  Alternatively, may be an nsIFile, a DownloadTarget object,
+   *                  or an object with the following properties:
+   *          {
+   *            path: String containing the path of the target file.
+   *          },
+   *          saver: String representing the class of the download operation.
+   *                 If omitted, defaults to "copy".  Alternatively, may be the
+   *                 serializable representation of a DownloadSaver object.
+   *        }
+   *
+   * @return {Promise}
+   * @resolves The newly created Download object.
+   * @rejects JavaScript exception.
+   */
+  createDownload: function D_createDownload(aProperties)
+  {
+    try {
+      return Promise.resolve(Download.fromSerializable(aProperties));
+    } catch (ex) {
+      return Promise.reject(ex);
+    }
+  },
+
+  /**
+   * Downloads data from a remote network location to a local file.
+   *
+   * This download method does not provide user interface, or the ability to
+   * cancel or restart the download programmatically.  For that, you should
+   * obtain a reference to a Download object using the createDownload function.
+   *
+   * Since the download cannot be restarted, any partially downloaded data will
+   * not be kept in case the download fails.
+   *
+   * @param aSource
+   *        String containing the URI for the download source.  Alternatively,
+   *        may be an nsIURI or a DownloadSource object.
+   * @param aTarget
+   *        String containing the path of the target file.  Alternatively, may
+   *        be an nsIFile or a DownloadTarget object.
+   * @param aOptions
+   *        An optional object used to control the behavior of this function.
+   *        You may pass an object with a subset of the following fields:
+   *        {
+   *          isPrivate: Indicates whether the download originated from a
+   *                     private window.
+   *        }
+   *
+   * @return {Promise}
+   * @resolves When the download has finished successfully.
+   * @rejects JavaScript exception if the download failed.
+   */
+  fetch: function (aSource, aTarget, aOptions) {
+    return this.createDownload({
+      source: aSource,
+      target: aTarget,
+    }).then(function D_SD_onSuccess(aDownload) {
+      if (aOptions && ("isPrivate" in aOptions)) {
+        aDownload.source.isPrivate = aOptions.isPrivate;
+      }
+      return aDownload.start();
+    });
+  },
+
+  /**
+   * Retrieves the specified type of DownloadList object.  There is one download
+   * list for each type, and this method always retrieves a reference to the
+   * same download list when called with the same argument.
+   *
+   * Calling this function may cause the list of public downloads to be reloaded
+   * from the previous session, if it wasn't loaded already.
+   *
+   * @param aType
+   *        This can be Downloads.PUBLIC, Downloads.PRIVATE, or Downloads.ALL.
+   *        Downloads added to the Downloads.PUBLIC and Downloads.PRIVATE lists
+   *        are reflected in the Downloads.ALL list, and downloads added to the
+   *        Downloads.ALL list are also added to either the Downloads.PUBLIC or
+   *        the Downloads.PRIVATE list based on their properties.
+   *
+   * @return {Promise}
+   * @resolves The requested DownloadList or DownloadCombinedList object.
+   * @rejects JavaScript exception.
+   */
+  getList: function (aType)
+  {
+    if (!this._promiseListsInitialized) {
+      this._promiseListsInitialized = Task.spawn(function* () {
+        let publicList = new DownloadList();
+        let privateList = new DownloadList();
+        let combinedList = new DownloadCombinedList(publicList, privateList);
+
+        try {
+          yield DownloadIntegration.addListObservers(publicList, false);
+          yield DownloadIntegration.addListObservers(privateList, true);
+          yield DownloadIntegration.initializePublicDownloadList(publicList);
+        } catch (ex) {
+          Cu.reportError(ex);
+        }
+
+        let publicSummary = yield this.getSummary(Downloads.PUBLIC);
+        let privateSummary = yield this.getSummary(Downloads.PRIVATE);
+        let combinedSummary = yield this.getSummary(Downloads.ALL);
+
+        yield publicSummary.bindToList(publicList);
+        yield privateSummary.bindToList(privateList);
+        yield combinedSummary.bindToList(combinedList);
+
+        this._lists[Downloads.PUBLIC] = publicList;
+        this._lists[Downloads.PRIVATE] = privateList;
+        this._lists[Downloads.ALL] = combinedList;
+      }.bind(this));
+    }
+
+    return this._promiseListsInitialized.then(() => this._lists[aType]);
+  },
+
+  /**
+   * Promise resolved when the initialization of the download lists has
+   * completed, or null if initialization has never been requested.
+   */
+  _promiseListsInitialized: null,
+
+  /**
+   * After initialization, this object is populated with one key for each type
+   * of download list that can be returned (Downloads.PUBLIC, Downloads.PRIVATE,
+   * or Downloads.ALL).  The values are the DownloadList objects.
+   */
+  _lists: {},
+
+  /**
+   * Retrieves the specified type of DownloadSummary object.  There is one
+   * download summary for each type, and this method always retrieves a
+   * reference to the same download summary when called with the same argument.
+   *
+   * Calling this function does not cause the list of public downloads to be
+   * reloaded from the previous session.  The summary will behave as if no
+   * downloads are present until the getList method is called.
+   *
+   * @param aType
+   *        This can be Downloads.PUBLIC, Downloads.PRIVATE, or Downloads.ALL.
+   *
+   * @return {Promise}
+   * @resolves The requested DownloadList or DownloadCombinedList object.
+   * @rejects JavaScript exception.
+   */
+  getSummary: function (aType)
+  {
+    if (aType != Downloads.PUBLIC && aType != Downloads.PRIVATE &&
+        aType != Downloads.ALL) {
+      throw new Error("Invalid aType argument.");
+    }
+
+    if (!(aType in this._summaries)) {
+      this._summaries[aType] = new DownloadSummary();
+    }
+
+    return Promise.resolve(this._summaries[aType]);
+  },
+
+  /**
+   * This object is populated by the getSummary method with one key for each
+   * type of object that can be returned (Downloads.PUBLIC, Downloads.PRIVATE,
+   * or Downloads.ALL).  The values are the DownloadSummary objects.
+   */
+  _summaries: {},
+
+  /**
+   * Returns the system downloads directory asynchronously.
+   *   Mac OSX:
+   *     User downloads directory
+   *   XP/2K:
+   *     My Documents/Downloads
+   *   Vista and others:
+   *     User downloads directory
+   *   Linux:
+   *     XDG user dir spec, with a fallback to Home/Downloads
+   *   Android:
+   *     standard downloads directory i.e. /sdcard
+   *
+   * @return {Promise}
+   * @resolves The downloads directory string path.
+   */
+  getSystemDownloadsDirectory: function D_getSystemDownloadsDirectory() {
+    return DownloadIntegration.getSystemDownloadsDirectory();
+  },
+
+  /**
+   * Returns the preferred downloads directory based on the user preferences
+   * in the current profile asynchronously.
+   *
+   * @return {Promise}
+   * @resolves The downloads directory string path.
+   */
+  getPreferredDownloadsDirectory: function D_getPreferredDownloadsDirectory() {
+    return DownloadIntegration.getPreferredDownloadsDirectory();
+  },
+
+  /**
+   * Returns the temporary directory where downloads are placed before the
+   * final location is chosen, or while the document is opened temporarily
+   * with an external application. This may or may not be the system temporary
+   * directory, based on the platform asynchronously.
+   *
+   * @return {Promise}
+   * @resolves The downloads directory string path.
+   */
+  getTemporaryDownloadsDirectory: function D_getTemporaryDownloadsDirectory() {
+    return DownloadIntegration.getTemporaryDownloadsDirectory();
+  },
+
+  /**
+   * Constructor for a DownloadError object.  When you catch an exception during
+   * a download, you can use this to verify if "ex instanceof Downloads.Error",
+   * before reading the exception properties with the error details.
+   */
+  Error: DownloadError,
+};
diff --git a/toolkit/components/jsdownloads/src/Downloads.manifest b/toolkit/components/jsdownloads/src/Downloads.manifest
new file mode 100644
index 000000000..03d4ed4a6
--- /dev/null
+++ b/toolkit/components/jsdownloads/src/Downloads.manifest
@@ -0,0 +1,2 @@
+component {1b4c85df-cbdd-4bb6-b04e-613caece083c} DownloadLegacy.js
+contract @mozilla.org/transfer;1 {1b4c85df-cbdd-4bb6-b04e-613caece083c}
diff --git a/toolkit/components/jsdownloads/src/moz.build b/toolkit/components/jsdownloads/src/moz.build
new file mode 100644
index 000000000..87abed62e
--- /dev/null
+++ b/toolkit/components/jsdownloads/src/moz.build
@@ -0,0 +1,31 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+SOURCES += [
+    'DownloadPlatform.cpp',
+]
+
+EXTRA_COMPONENTS += [
+    'DownloadLegacy.js',
+    'Downloads.manifest',
+]
+
+EXTRA_JS_MODULES += [
+    'DownloadCore.jsm',
+    'DownloadImport.jsm',
+    'DownloadList.jsm',
+    'Downloads.jsm',
+    'DownloadStore.jsm',
+    'DownloadUIHelper.jsm',
+]
+
+EXTRA_PP_JS_MODULES += [
+    'DownloadIntegration.jsm',
+]
+
+FINAL_LIBRARY = 'xul'
+
+CXXFLAGS += CONFIG['TK_CFLAGS']