Bug 1665437 - [marionette] Fix race between "WebDriver:CloseChromeWindow" and next browsing context check. r=marionette-reviewers,maja_zf

Similar to closing a tab the internal browsing contexts
need to be nullified. This is necessary because browsing
contexts are asynchronously discarded and garbage collected.

Also the "unload" event as currently used to wait for the
chrome window to be closed fires too early. Instead the
"xul-window-destroyed" observer notification needs to be used.

Differential Revision: https://phabricator.services.mozilla.com/D91296

testing/marionette/browser.js

@@ -275,15 +275,14 @@ browser.Context = class {
    * @return {Promise}
    *     A promise which is resolved when the current window has been closed.
    */
-  closeWindow() {
-    let destroyed = new MessageManagerDestroyedPromise(
-      this.window.messageManager
-    );
-    let unloaded = waitForEvent(this.window, "unload");
+  async closeWindow() {
+    const destroyed = waitForObserverTopic("xul-window-destroyed", {
+      checkFn: () => this.window && this.window.closed,
+    });
 
     this.window.close();
 
-    return Promise.all([destroyed, unloaded]);
+    return destroyed;
   }
 
   /**

testing/marionette/driver.js

@@ -2936,6 +2936,9 @@ GeckoDriver.prototype.closeChromeWindow = async function() {
   }
 
   await this.curBrowser.closeWindow();
+  this.chromeBrowsingContext = null;
+  this.contentBrowsingContext = null;
+
   return this.chromeWindowHandles.map(String);
 };
 

testing/marionette/harness/marionette_harness/tests/unit/test_window_status_content.py

@@ -2,7 +2,7 @@
 # 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/.
 
-from __future__ import absolute_import
+from __future__ import absolute_import, print_function
 
 from marionette_driver import By
 from marionette_driver.errors import NoSuchWindowException
@@ -27,6 +27,7 @@ class TestNoSuchWindowContent(WindowManagerMixin, MarionetteTestCase):
 
         # When closing a browser window both handles are not available
         for context in ("chrome", "content"):
+            print("Testing handles with context {}".format(context))
             with self.marionette.using_context(context):
                 with self.assertRaises(NoSuchWindowException):
                     self.marionette.current_chrome_window_handle