commit 364a72e0c75f46f913f894c3e2fe3a7aa24f6dcd
author Nate Chapin <japhet@chromium.org> Mon Nov 27 19:56:59 2023
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Mon Nov 27 19:56:59 2023
tree ca8818b5120fbed43f1f656de4e44703dbaa41e5
parent 2650ebec827009ea46a7239649eb080a77523a4e

Fire the navigate event earlier for cross-document traversals

This earlier timing ensures that we fire the navigate event in the old
document when a traversal is served from the bfcache, and is more consistent with non-history cross-document navigate events.

Currently, cross-document traversals fire the navigate event at the
last possible time: during commit in the renderer, the navigate event
is fired in the old document immediately before it is unloaded. The
navigate event is not allowed to cancel or intercept a cross-document
traversal, otherwise this timing would be too late. We did not
reach a firm conclusion on when to fire the navigate event for
cross-document traversals during the design of the Navigation API
(see https://github.com/WICG/navigation-api/issues/207), and this
was the latest of the options considered.

This timing has two problems:
1. Traversals served by the back forward cache don't "commit". So
   the navigate event is erroneously omitted.
2. The navigate event fires after redirects, where for other
   cross-document navigations, it fires before redirects.

This CL adds plumbing for the browser to trigger the navigate event
to fire in the renderer in the cross-document traversal case, and
moves the time of the navigate event earlier. It now fires after
the browser process has decided to allow the traversal to start
(i.e., after beforeunload has been fired in any relevant frames, and
after start throttles). In the cross-document traversal case where
the navigation is not served from bfcache, this will fire the
navigate event in parallel with the network request (which is ok
because the navigate event can't intercept or cancel the navigation,
this timing would not be permissible for other navigation types where
the navigate event has more power over the navigation). In the case
where no network request is needed (bfcache, about:blank, etc.), the
navigate event task gets sent to the renderer immediately before the
commit/activation task.

Bug: 1475907
Change-Id: I1ef7337e2d85f9cdbfc0110f9f4fe3bcd4dea75d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5011394
Reviewed-by: Domenic Denicola <domenic@chromium.org>
Commit-Queue: Nate Chapin <japhet@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Reviewed-by: Will Harris <wfh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1229455}