[Webkit-unassigned] [Bug 183386] LayoutTests/http/tests/navigation/page-cache-iframe-provisional-load.html fails with async policy delegate

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=183386

--- Comment #5 from Chris Dumez <cdumez at apple.com> ---
(In reply to Danyao Wang from comment #4)
> Turns out my initial analysis was wrong and we can't use
> delegateIsDecidingNavigationPolicy().
> 
> What happens is that the decide policy process for the main frame and the
> subframe are interleaved. So when
> FrameLoader::continueLoadAfterNavigationPolicy() is called for the main
> frame, it calls FrameLoader::stopAllLoaders(), which invalidates the
> in-progress policy check on the subframe. This triggers
> FrameLoader::continueLoadAfterNavigationPlicy() on the subframe with
> PolicyAction::Ignore. Later when PageCache::addIfCacheable() is called after
> main frame commits the provisional navigation, the sub frame load has
> already been cancelled, so it is neither in decide policy nor provisional
> load. This leads to PageCache deciding to cache the page.
> 
> With sync policy delegate, the main policy decision is fully finished before
> subframe enters into decide policy. The subframe loader gets a
> PolicyAction::Use result from the UIProcess and transitions to
> FrameStateProvisionalLoad before the main frame commits the provisional
> navigation.
> 
> It seems to me that canceling outstanding subframe policy checks when main
> frame commits its provisional navigation makes sense. So despite the
> difference in timing, I think the behavior here is working as intended.
> 
> I'm less sure if the page in such a state should be cached. "No" seems to
> make sense, because the page is now in a broken state with one of its
> subframe load interrupted and I assume that's why we check for
> FrameStateProvisionalLoad. Capturing this specific case will be a bit messy,
> because we'd need to pass a cancelation reason into
> FrameLoader::stopAllLoaders().
> 
> Chris - what do you think?

I believe this is the check that is supposed to make sure we don't put broken content into PageCache:
if (!documentLoader->mainDocumentError().isNull()) {
        PCLOG("   -Main document has an error");
        logPageCacheFailureDiagnosticMessage(diagnosticLoggingClient, DiagnosticLoggingKeys::mainDocumentErrorKey());

        if (documentLoader->mainDocumentError().isCancellation() && documentLoader->subresourceLoadersArePageCacheAcceptable())
            PCLOG("    -But, it was a cancellation and all loaders during the cancelation were loading images or XHR.");
        else
            isCacheable = false;
    }

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