diff -r 000000000000 -r 6474c204b198 dom/downloads/src/DownloadsAPI.jsm
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/downloads/src/DownloadsAPI.jsm	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,268 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+
+this.EXPORTED_SYMBOLS = [];
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/Downloads.jsm");
+Cu.import("resource://gre/modules/Task.jsm");
+
+XPCOMUtils.defineLazyServiceGetter(this, "ppmm",
+                                   "@mozilla.org/parentprocessmessagemanager;1",
+                                   "nsIMessageBroadcaster");
+
+function debug(aStr) {
+#ifdef MOZ_DEBUG
+  dump("-*- DownloadsAPI.jsm : " + aStr + "\n");
+#endif
+}
+
+function sendPromiseMessage(aMm, aMessageName, aData, aError) {
+  debug("sendPromiseMessage " + aMessageName);
+  let msg = {
+    id: aData.id,
+    promiseId: aData.promiseId
+  };
+
+  if (aError) {
+    msg.error = aError;
+  }
+
+  aMm.sendAsyncMessage(aMessageName, msg);
+}
+
+let DownloadsAPI = {
+  init: function() {
+    debug("init");
+
+    this._ids = new WeakMap(); // Maps toolkit download objects to ids.
+    this._index = {};          // Maps ids to downloads.
+
+    ["Downloads:GetList",
+     "Downloads:ClearAllDone",
+     "Downloads:Remove",
+     "Downloads:Pause",
+     "Downloads:Resume"].forEach((msgName) => {
+      ppmm.addMessageListener(msgName, this);
+    });
+
+    let self = this;
+    Task.spawn(function () {
+      let list = yield Downloads.getList(Downloads.ALL);
+      yield list.addView(self);
+
+      debug("view added to download list.");
+    }).then(null, Components.utils.reportError);
+
+    this._currentId = 0;
+  },
+
+  /**
+    * Returns a unique id for each download, hashing the url and the path.
+    */
+  downloadId: function(aDownload) {
+    let id = this._ids.get(aDownload, null);
+    if (!id) {
+      id = "download-" + this._currentId++;
+      this._ids.set(aDownload, id);
+      this._index[id] = aDownload;
+    }
+    return id;
+  },
+
+  getDownloadById: function(aId) {
+    return this._index[aId];
+  },
+
+  /**
+    * Converts a download object into a plain json object that we'll
+    * send to the DOM side.
+    */
+  jsonDownload: function(aDownload) {
+    let res = {
+      totalBytes: aDownload.totalBytes,
+      currentBytes: aDownload.currentBytes,
+      url: aDownload.source.url,
+      path: aDownload.target.path,
+      contentType: aDownload.contentType,
+      startTime: aDownload.startTime.getTime()
+    };
+
+    if (aDownload.error) {
+      res.error = aDownload.error;
+    }
+
+    res.id = this.downloadId(aDownload);
+
+    // The state of the download. Can be any of "downloading", "stopped",
+    // "succeeded", finalized".
+
+    // Default to "stopped"
+    res.state = "stopped";
+    if (!aDownload.stopped &&
+        !aDownload.canceled &&
+        !aDownload.succeeded &&
+        !aDownload.DownloadError) {
+      res.state = "downloading";
+    } else if (aDownload.succeeded) {
+      res.state = "succeeded";
+    }
+    return res;
+  },
+
+  /**
+    * download view methods.
+    */
+  onDownloadAdded: function(aDownload) {
+    let download = this.jsonDownload(aDownload);
+    debug("onDownloadAdded " + uneval(download));
+    ppmm.broadcastAsyncMessage("Downloads:Added", download);
+  },
+
+  onDownloadRemoved: function(aDownload) {
+    let download = this.jsonDownload(aDownload);
+    download.state = "finalized";
+    debug("onDownloadRemoved " + uneval(download));
+    ppmm.broadcastAsyncMessage("Downloads:Removed", download);
+    this._index[this._ids.get(aDownload)] = null;
+    this._ids.delete(aDownload);
+  },
+
+  onDownloadChanged: function(aDownload) {
+    let download = this.jsonDownload(aDownload);
+    debug("onDownloadChanged " + uneval(download));
+    ppmm.broadcastAsyncMessage("Downloads:Changed", download);
+  },
+
+  receiveMessage: function(aMessage) {
+    if (!aMessage.target.assertPermission("downloads")) {
+      debug("No 'downloads' permission!");
+      return;
+    }
+
+    debug("message: " + aMessage.name);
+
+    switch (aMessage.name) {
+    case "Downloads:GetList":
+      this.getList(aMessage.data, aMessage.target);
+      break;
+    case "Downloads:ClearAllDone":
+      this.clearAllDone(aMessage.data, aMessage.target);
+      break;
+    case "Downloads:Remove":
+      this.remove(aMessage.data, aMessage.target);
+      break;
+    case "Downloads:Pause":
+      this.pause(aMessage.data, aMessage.target);
+      break;
+    case "Downloads:Resume":
+      this.resume(aMessage.data, aMessage.target);
+      break;
+    default:
+      debug("Invalid message: " + aMessage.name);
+    }
+  },
+
+  getList: function(aData, aMm) {
+    debug("getList called!");
+    let self = this;
+    Task.spawn(function () {
+      let list = yield Downloads.getList(Downloads.ALL);
+      let downloads = yield list.getAll();
+      let res = [];
+      downloads.forEach((aDownload) => {
+        res.push(self.jsonDownload(aDownload));
+      });
+      aMm.sendAsyncMessage("Downloads:GetList:Return", res);
+    }).then(null, Components.utils.reportError);
+  },
+
+  clearAllDone: function(aData, aMm) {
+    debug("clearAllDone called!");
+    let self = this;
+    Task.spawn(function () {
+      let list = yield Downloads.getList(Downloads.ALL);
+      yield list.removeFinished();
+      list = yield Downloads.getList(Downloads.ALL);
+      let downloads = yield list.getAll();
+      let res = [];
+      downloads.forEach((aDownload) => {
+        res.push(self.jsonDownload(aDownload));
+      });
+      aMm.sendAsyncMessage("Downloads:ClearAllDone:Return", res);
+    }).then(null, Components.utils.reportError);
+  },
+
+  remove: function(aData, aMm) {
+    debug("remove id " + aData.id);
+    let download = this.getDownloadById(aData.id);
+    if (!download) {
+      sendPromiseMessage(aMm, "Downloads:Remove:Return",
+                         aData, "NoSuchDownload");
+      return;
+    }
+
+    Task.spawn(function() {
+      yield download.finalize(true);
+      let list = yield Downloads.getList(Downloads.ALL);
+      yield list.remove(download);
+    }).then(
+      function() {
+        sendPromiseMessage(aMm, "Downloads:Remove:Return", aData);
+      },
+      function() {
+        sendPromiseMessage(aMm, "Downloads:Remove:Return",
+                           aData, "RemoveError");
+      }
+    );
+  },
+
+  pause: function(aData, aMm) {
+    debug("pause id " + aData.id);
+    let download = this.getDownloadById(aData.id);
+    if (!download) {
+      sendPromiseMessage(aMm, "Downloads:Pause:Return",
+                         aData, "NoSuchDownload");
+      return;
+    }
+
+    download.cancel().then(
+      function() {
+        sendPromiseMessage(aMm, "Downloads:Pause:Return", aData);
+      },
+      function() {
+        sendPromiseMessage(aMm, "Downloads:Pause:Return",
+                           aData, "PauseError");
+      }
+    );
+  },
+
+  resume: function(aData, aMm) {
+    debug("resume id " + aData.id);
+    let download = this.getDownloadById(aData.id);
+    if (!download) {
+      sendPromiseMessage(aMm, "Downloads:Resume:Return",
+                         aData, "NoSuchDownload");
+      return;
+    }
+
+    download.start().then(
+      function() {
+        sendPromiseMessage(aMm, "Downloads:Resume:Return", aData);
+      },
+      function() {
+        sendPromiseMessage(aMm, "Downloads:Resume:Return",
+                           aData, "ResumeError");
+      }
+    );
+  }
+};
+
+DownloadsAPI.init();