salvagable when unloading a document with pagehide listener

[zcorpan]

See web-platform-tests/wpt#11294

I have not investigated much about what the browser behavior really is, but for this test it seems salvagable should be false (or at least the setTimeout doesn't survive the navigation in browsers).

[annevk]

Nothing in https://searchfox.org/mozilla-central/source/dom/base/nsDocument.cpp#7997 seems to support this though. So there must be a different reason.

[zcorpan]

@bzbarsky any clue?

[bzbarsky]

I would really appreciate a clearer description of what you're asking. Which of the tests web-platform-tests/wpt#11294 touches are we talking about here? Which of the multiple setTimeout calls in those tests are we talking about?

[bzbarsky]

In particular, if we're talking about html/browsers/browsing-the-web/unloading-documents/unload/manual-001.html then I do see "PASS" when I go back in that test, in Firefox.

So are you talking about html/browsers/browsing-the-web/unloading-documents/unload/006-1.html then?

[zcorpan]

Sorry, html/browsers/browsing-the-web/unloading-documents/unload/006-1.html , this timeout

   setTimeout(function() {
-               parent.t.done()
+               parent.t.step_func(function() { assert_unreached('setTimeout survived navigatoin'); })
              }, 1000);

[bzbarsky]

Ah, thank you for explaining.

In Firefox only toplevel navigations get bfcached. So if navigation is happening in a subframe, as here, the document will never be considered salvagable. This seems to be a violation of the spec, because as far as I can tell the spec requires bfcaching in all cases(!). That seems like a spec bug. Bfcaching is not a feature that should be required.

[zcorpan]

Ok, turning off bfcache for non-top-level BCs seems reasonably simple to fix in the spec.

[bzbarsky]

I think the spec should allow, but not require, bfcache. Period. Browsers should be free to not bfcache for whatever reason they want to...

[zcorpan]

Sure, it can do that also. But if all browsers agree to disable it for iframes, then the spec can codify that, and have bfcache be optional just for top-level.

[bzbarsky]

I guess. The only reason Firefox didn't enable it for iframes was that it was more work that we haven't found the time/desire to do yet.... There's no conceptual reason to forbid it.