[fetch-later] Fix quota allocation for sandbox iframes.

When the [`reserve deferred-fetch quota`][1] step for a iframe, i.e. `GetContainerDeferredFetchPolicyOnNavigation()`, is triggered, it
requires a `originToNavigateTo` of the target url. If the iframe is
sandboxed, its final url origin after navigation would be "null" in
terms of parent's view. However, it is not avaiable at this step which
is under `FrameLoader::StartNavigation()`.

This CL manually provides such info using `sandbox_flags` from the
owner (iframe)'s frame policy, and pass that into
`GetContainerDeferredFetchPolicyOnNavigation()`.


[1]: https://fetch.spec.whatwg.org/#reserve-deferred-fetch-quota

Bug: 410528357
Change-Id: Ia1041e486f55e56b1cced64affd124de63a264a4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6905117
Commit-Queue: Ming-Ying Chung <mych@chromium.org>
Reviewed-by: Adam Rice <ricea@chromium.org>
Reviewed-by: Nate Chapin <japhet@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1513441}