Remove expect calls in service worker manager thread

[creativcoder]

An intermittent timeout was seen in #12516 , caused by panic of ServiceWorkerManager thread on reception of messages from resource thread. This PR amends things to not have the ServiceWorkerManager thread panic in such situation.
cc @jdm

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• ./mach build -d does not report any errors
• ./mach test-tidy does not report any errors
• These changes fix #Intermittent timeout in /eventsource/dedicated-worker/eventsource-prototype.htm and /eventsource/dedicated-worker/eventsource-url.htm #12516 (github issue number if applicable).

• These changes do not require tests because its an "intermittent fix"

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This change is

[highfive]

Heads up! This PR modifies the following files:

• @KiChjang: components/script/serviceworker_manager.rs

[highfive]

Warning

• These commits modify unsafe code. Please review it carefully!
• These commits modify script code, but no tests are modified. Please consider adding a test!

[nox]

Thanks for the contribution. I want a couple of changes but that's all.

-S-awaiting-review +S-needs-code-changes

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Reviewed 1 of 1 files at r1.
Review status: all files reviewed at latest revision, 3 unresolved discussions, some commit checks failed.

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a discussion (no related file):
It took me quite a bit of time to realise that it was about removing the two expect calls in receive_message.

Could you reword the commit message to make that crystal clear?

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components/script/serviceworker_manager.rs, line 107 [r1] (raw file):

       while self.receive_message() {
        // process message
       }

Please restore the two additional handle_message methods and do something like this:

fn handle_message(&mut self) {
    while let Ok(message) = self.receive_message() {
        let should_continue = match message {
            Message::FromConstellation(msg) => {
                self.handle_message_from_constellation(msg)
            },
            Message::FromResource(msg) => {
                self.handle_message_from_resource(msg)
            }
        };
        if !should_continue {
            break;
        }
    }
}

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components/script/serviceworker_manager.rs, line 160 [r1] (raw file):

        } else {
            panic!("Unexpected select result");
        }

I'm pretty sure you can continue to use select! here.

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Comments from Reviewable

[creativcoder]

Review status: 0 of 1 files reviewed at latest revision, 3 unresolved discussions.

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a discussion (no related file):

Previously, nox (Anthony Ramine) wrote…

It took me quite a bit of time to realise that it was about removing the two expect calls in receive_message.

Could you reword the commit message to make that crystal clear?

Done

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Comments from Reviewable

[nox]

-S-awaiting-review +S-needs-code-changes

One last nit and I'll r+ it. Thanks again!

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Reviewed 1 of 1 files at r2.
Review status: all files reviewed at latest revision, 1 unresolved discussion.

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components/script/serviceworker_manager.rs, line 163 [r2] (raw file):

        select! {
            msg = msg_from_constellation.recv() => Ok(Message::FromConstellation(try!(msg))),
            msg = msg_from_resource.recv() => Ok(Message::FromResource(try!(msg)))

Nit: for these you can write msg.map(Message::FromConstellation) and msg.map(Message::FromResource).

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Comments from Reviewable

[nox]

bors-servo r+

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Reviewed 1 of 1 files at r3.
Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable

[nox]

...

@bors-servo r+

[bors-servo]

📌 Commit 66c04a0 has been approved by nox

[bors-servo]

⌛ Testing commit 66c04a0 with merge 07a0c2f...

[bors-servo]

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