Heads up! This PR modifies the following files:

• @KiChjang: components/script/script_thread.rs, components/script/dom/document.rs, components/script/dom/servoparser/mod.rs, components/script/document_loader.rs

@bors-servo try

⌛ Trying commit d97ae85 with merge 45ab9d5...

💔 Test failed - mac-rel-wpt1

@bors-servo try

⌛ Trying commit 19bd43f with merge c8cdccb...

💔 Test failed - linux-rel-wpt

☔ The latest upstream changes (presumably #13750) made this pull request unmergeable. Please resolve the merge conflicts.

Status update: investigating the timeout in /_mozilla/mozilla/referrer-policy/unset-referrer-policy/meta-referrer/same-origin/http-https/iframe-tag/upgrade-protocol.keep-origin-redirect.http.html. Apparently the load event is not dispatched at the iframe created in queryIframe.

The issue lies within this lovely piece of code:

        let mut ssl_error = None;
        let metadata = match meta_result {
            Ok(meta) => Some(meta),
            Err(NetworkError::SslValidation(url, reason)) => {
                ssl_error = Some(reason);
                let mut meta = Metadata::default(url);
                let mime: Option<Mime> = "text/html".parse().ok();
                meta.set_content_type(mime.as_ref());
                Some(meta)
            },
            Err(_) => None,
        };

With the old stack, we get Err(NetworkError::SslValidation(..)), create a new Metadata and go on our merry way. With the fetch stack, we get some other Err(..) value, ScriptThread::page_headers_available notices metadata is None and returns None itself, so we bail out without a parser object, and the load event is never fired.

@jdm, thoughts?

I propose that we modify the ResponseType::Error variant to store a NetworkError value, and modify the block in http_network_fetch that gets an Err value from obtain_response to turn the response into an error response that contains the actual error that was returned from the network stack. This will allow the metadata method to return an error that was extracted from the error response, rather than just returning an internal error.

Rebased; planning to look into your suggestion tomorrow. Thanks!

@bors-servo try

⌛ Trying commit addec42 with merge 6a83c01...

@bors-servo r=jdm

📌 Commit c7636a2 has been approved by jdm

⌛ Testing commit c7636a2 with merge ba2fb4e...

☀️ Test successful - arm32, arm64, linux-dev, linux-rel-css, linux-rel-wpt, mac-dev-unit, mac-rel-css, mac-rel-wpt1, mac-rel-wpt2, windows-dev