Improve Synchronizer functionality

lib/downloader.js

Index: lib/downloader.js
===================================================================
--- a/lib/downloader.js
+++ b/lib/downloader.js
@@ -63,17 +63,17 @@ Downloader.prototype =
    */
   dataSource: null,
 
   /**
    * Maximal time interval that the checks can be left out until the soft
    * expiration interval increases.
    * @type Integer
    */
-  maxAbsenseInterval: 1 * MILLIS_IN_DAY,
+  maxAbsenceInterval: 1 * MILLIS_IN_DAY,
 
   /**
    * Minimal time interval before retrying a download after an error.
    * @type Integer
    */
   minRetryInterval: 1 * MILLIS_IN_DAY,
 
   /**
@@ -117,17 +117,17 @@ Downloader.prototype =
   /**
    * Checks whether anything needs downloading.
    */
   _doCheck: function()
   {
     let now = Date.now();
     for each (let downloadable in this.dataSource())
     {
-      if (downloadable.lastCheck && now - downloadable.lastCheck > this.maxAbsenseInterval)
+      if (downloadable.lastCheck && now - downloadable.lastCheck > this.maxAbsenceInterval)
       {
         // No checks for a long time interval - user must have been offline, e.g.
         // during a weekend. Increase soft expiration to prevent load peaks on the
         // server.
         downloadable.softExpiration += now - downloadable.lastCheck;
       }
       downloadable.lastCheck = now;
 
@@ -166,20 +166,19 @@ Downloader.prototype =
    * Checks whether an address is currently being downloaded.
    */
   isDownloading: function(/**String*/ url) /**Boolean*/
   {
     return url in this._downloading;
   },
 
   /**
-   * Starts a download.
-   * @param {Downloadable} url  the object to be downloaded
+   * Starts downloading for an object.
    */
-  download: function(downloadable)
+  download: function(/**Downloadable*/ downloadable)
   {
     // Make sure to detach download from the current execution context
     Utils.runAsync(this._download.bind(this, downloadable, 0));
   },
 
   /**
    * Generates the real download URL for an object by appending various
    * parameters.
@@ -199,59 +198,59 @@ Downloader.prototype =
         "&platform=" + encodeURIComponent(platform) +
         "&platformVersion=" + encodeURIComponent(platformVersion) +
         "&lastVersion=" + encodeURIComponent(downloadable.lastVersion);
     return url;
   },
 
   _download: function(downloadable, redirects)
   {
-    if (downloadable.url in this._downloading)
+    if (this.isDownloading(downloadable.url))
       return;
 
-    let downloadURL = this.getDownloadUrl(downloadable);
+    let downloadUrl = this.getDownloadUrl(downloadable);
     let request = null;
 
     let errorCallback = function errorCallback(error)
     {
       let channelStatus = -1;
       try
       {
         channelStatus = request.channel.status;
       } catch (e) {}
 
       let responseStatus = request.status;
 
       Cu.reportError("Adblock Plus: Downloading URL " + downloadable.url + " failed (" + error + ")\n" +
-                     "Download address: " + downloadURL + "\n" +
+                     "Download address: " + downloadUrl + "\n" +
                      "Channel status: " + channelStatus + "\n" +
                      "Server response: " + responseStatus);
 
       if (this.onDownloadError)
       {
         // Allow one extra redirect if the error handler gives us a redirect URL
         let redirectCallback = null;
         if (redirects <= this.maxRedirects)
         {
           redirectCallback = function redirectCallback(url)
           {
             downloadable.redirectURL = url;
             this._download(downloadable, redirects + 1);
           }.bind(this);
         }
 
-        this.onDownloadError(downloadable, downloadURL, error, channelStatus, responseStatus, redirectCallback);
+        this.onDownloadError(downloadable, downloadUrl, error, channelStatus, responseStatus, redirectCallback);
       }
     }.bind(this);
 
     try
     {
       request = new XMLHttpRequest();
       request.mozBackgroundRequest = true;
-      request.open("GET", downloadURL);
+      request.open("GET", downloadUrl);
     }
     catch (e)
     {
       errorCallback("synchronize_invalid_url");
       return;
     }
 
     try {
@@ -299,20 +298,21 @@ Downloader.prototype =
         else
         {
           downloadable.redirectURL = url;
           this._download(downloadable, redirects + 1);
         }
       }.bind(this));
     }.bind(this), false);
 
+    request.send(null);
+
     this._downloading[downloadable.url] = true;
     if (this.onDownloadStarted)
       this.onDownloadStarted(downloadable);
-    request.send(null);
   },
 
   /**
    * Produces a soft and a hard expiration interval for a given supplied
    * expiration interval.
    * @return {Array} soft and hard expiration interval
    */
   processExpirationInterval: function(/**Integer*/ interval)