Issue 3815 - Fix TabAllocator. Now it returns tab with initialized outerWindowID

lib/crawler.js

Index: lib/crawler.js
diff --git a/lib/crawler.js b/lib/crawler.js
index 7bc28dbbe75187a1a752583c81d5c638a24c98ca..8e7144acee6667440528cb34e62d419bee7aa784 100644
--- a/lib/crawler.js
+++ b/lib/crawler.js
@@ -25,7 +25,7 @@ let {FilterNotifier} = abprequire("filterNotifier");
 let {FilterStorage} = abprequire("filterStorage");
 
 /**
- * Creates a pool of tabs and allocates them to tasks on request.
+ * Allocates tabs on request but not more than maxtabs at the same time.
  *
  * @param {tabbrowser} browser
  *    The tabbed browser where tabs should be created
@@ -35,33 +35,63 @@ let {FilterStorage} = abprequire("filterStorage");
  */
 function TabAllocator(browser, maxtabs)
 {
-  browser.removeAllTabsBut(browser.tabs[0])
-
-  this._tabs = [];
-  for (let i = 0; i < maxtabs; i++)
-    this._tabs.push(browser.addTab("about:blank"));
-
-  browser.removeTab(browser.tabs[0]);
-
-  this._deferred = [];
+  this._browser = browser;
+  this._tabs = 0;
+  this._maxtabs = maxtabs;
+  // The queue containing resolve functions of promises waiting for a tab.
+  this._resolvers = [];
+  // Keep at least one tab alive to prevent browser from closing itself.
+  this._tabKeepingWindowAlive = this._browser.tabs[0];
+  this._browser.removeAllTabsBut(this._tabKeepingWindowAlive);
 }
 TabAllocator.prototype = {
+  _removeTabKeepingWindowAlive: function()
+  {
+    if (!this._tabKeepingWindowAlive)
+      return;
+    this._browser.removeTab(this._tabKeepingWindowAlive);
+    delete this._tabKeepingWindowAlive;
+  },
+
   /**
-   * Returns a promise that will resolve into a tab once a tab can be allocated.
-   * The tab cannot be used by other tasks until releaseTab() is called.
+   * Creates a blank tab in this._browser.
    *
-   * @result {Promise}
+   * @return {Promise.<tab>} promise which resolves once the tab is fully initialized.
    */
-  getTab: function()
+  _createTab: function()
   {
-    if (this._tabs.length)
-      return this._tabs.shift();
-    else
+    this._tabs++;
+    let tab = this._browser.addTab("about:blank");
+    if (tab.linkedBrowser.outerWindowID)
     {
-      let deferred = Promise.defer();
-      this._deferred.push(deferred);
-      return deferred.promise;
+      this._removeTabKeepingWindowAlive();
+      return Promise.resolve(tab);
     }
+    return new Promise((resolve, reject) =>
+    {
+      let onBrowserInit = (msg) =>
+      {
+        tab.linkedBrowser.messageManager.removeMessageListener("Browser:Init", onBrowserInit);
+        this._removeTabKeepingWindowAlive();
+        resolve(tab);
+      };
+      // "Browser:Init" message is sent once the browser is ready, see
+      // https://bugzil.la/1256602#c1
+      tab.linkedBrowser.messageManager.addMessageListener("Browser:Init", onBrowserInit);
+    });
+  },
+
+  /**
+   * Returns a promise that will resolve into a tab once a tab is allocated.
+   * The tab cannot be used by other tasks until releaseTab() is called.
+   *
+   * @result {Promise.<tab>}
+   */
+  getTab: function()
+  {
+    if (this._tabs < this._maxtabs)
+      return this._createTab();
+    return new Promise((resolve, reject) => this._resolvers.push(resolve));
   },
 
   /**
@@ -71,15 +101,23 @@ TabAllocator.prototype = {
    */
   releaseTab: function(tab)
   {
-    let browser = tab.parentNode.tabbrowser;
-    browser.removeTab(tab);
-    tab = browser.addTab("about:blank");
-
-    if (this._deferred.length)
-      this._deferred.shift().resolve(tab);
+    // If we are about to close last tab don't close it immediately to keep
+    // the window alive. It will be closed when a new tab is created.
+    if (this._tabs > 1)
+      this._browser.removeTab(tab);
     else
-      this._tabs.push(tab);
-  }
+    {
+      // navigate away from early opened URL
+      tab.linkedBrowser.loadURI('about:blank', null, null);
+      this._tabKeepingWindowAlive = tab;
+    }
+
+    this._tabs--;
+    if (this._resolvers.length && this._tabs < this._maxtabs)
+    {
+      this._resolvers.shift()(this._createTab());
+    }
+  },
 };
 
 /**
@@ -231,8 +269,8 @@ function run(window, urls, timeout, maxtabs, targetURL, onDone)
 exports.run = run;
 
 /**
- * Spawns a {Task} task to crawl each url from `urls` argument and calls
- * `onDone` when all tasks are finished.
+ * Spawns a {Task} task to crawl each url from urls argument and calls
+ * onDone when all tasks are finished.
  * @param {Window} window
  *   The browser window we're operating in
  * @param {String[]} urls