Fix input.insert_mode.auto_load race / test_auto_load flakiness

Fixes #8145, see #5390.

As long as we don't have a solution to get notified about focus happening
(#2471 possibly?), it looks like there is no better way to get notified
about this, so a delay will need to do for now.

doc/changelog.asciidoc

@@ -32,6 +32,12 @@ Changed
   `:quickmark-*`, `:bookmark-*`, `:tab-take` and `:tab-select` (for the quick
   and bookmark categories). (#7955)
 
+Fixed
+~~~~~
+
+- `input.insert_mode.auto_load` sometimes not triggering due to a race
+  condition.
+
 [[v3.1.1]]
 v3.1.1 (unreleased)
 -------------------

qutebrowser/browser/browsertab.py

@@ -14,7 +14,7 @@ from typing import (cast, TYPE_CHECKING, Any, Callable, Iterable, List, Optional
 
 from qutebrowser.qt import machinery
 from qutebrowser.qt.core import (pyqtSignal, pyqtSlot, QUrl, QObject, QSizeF, Qt,
-                          QEvent, QPoint, QRect)
+                          QEvent, QPoint, QRect, QTimer)
 from qutebrowser.qt.gui import QKeyEvent, QIcon, QPixmap
 from qutebrowser.qt.widgets import QApplication, QWidget
 from qutebrowser.qt.printsupport import QPrintDialog, QPrinter
@@ -902,7 +902,13 @@ class AbstractTabPrivate:
                 modeman.enter(self._tab.win_id, usertypes.KeyMode.insert,
                               'load finished', only_if_normal=True)
 
-        self._tab.elements.find_focused(_auto_insert_mode_cb)
+        # There seems to be a race between loadFinished being called,
+        # and the autoload attribute on websites actually focusing anything.
+        # Thus, we delay this by a bit. Locally, a delay of 13ms caused no races
+        # with 5000 test reruns (even with simultaneous CPU stress testing),
+        # so 65ms should be a safe bet and still not be too noticeable.
+        QTimer.singleShot(
+            65, lambda: self._tab.elements.find_focused(_auto_insert_mode_cb))
 
     def clear_ssl_errors(self) -> None:
         raise NotImplementedError

tests/end2end/data/insert_mode_settings/html/autofocus.html

@@ -10,6 +10,9 @@
               elem.addEventListener('input', function() {
                   console.log("contents: " + elem.value);
               });
+              elem.addEventListener('focus', function() {
+                  console.log("autofocus element focused");
+              });
           }
         </script>
     </head>

tests/end2end/test_insert_mode.py

@@ -43,7 +43,6 @@ def test_insert_mode(file_name, elem_id, source, input_text, zoom,
     (True, False, True),  # enabled and foreground tab
     (True, True, False),  # background tab
 ])
-@pytest.mark.flaky
 def test_auto_load(quteproc, auto_load, background, insert_mode):
     quteproc.set_setting('input.insert_mode.auto_load', str(auto_load))
     url_path = 'data/insert_mode_settings/html/autofocus.html'