Implement HTMLSelectElement.{multiple, name, size} (fixes #6017)

[Jinwoo-Song]

r? @jdm
cc @yichoi

[hoppipolla-critic-bot]

Critic review: https://critic.hoppipolla.co.uk/r/4973

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[Ms2ger]

@bors-servo: r+

[bors-servo]

📌 Commit 656a8ee has been approved by Ms2ger

[bors-servo]

⌛ Testing commit 656a8ee with merge 396a0de...

[bors-servo]

💔 Test failed - mac2

[Jinwoo-Song]

The failing test case seems not to be related to this patch. :( What should I do?

failures:

---- hide_after_create.html == hide_after_create_ref.html stdout ----
thread 'hide_after_create.html == hide_after_create_ref.html' panicked at 'rendering difference: /tmp/servo-reftest-000096-diff.png', ../../tests/reftest.rs:335

stack backtrace:
1: 0x101896bef - sys::backtrace::write::h6990067d88907b48zVr
2: 0x10189aca0 - panicking::on_panic::he976cdbadffd9e1bEVv
3: 0x10187bde5 - rt::unwind::begin_unwind_inner::ha519446d83876aa8nDv
4: 0x10187c57c - rt::unwind::begin_unwind_fmt::h15c2d4adf8e8ecdatCv
5: 0x101810904 - check_reftest::h50e372ab33546d9fiKa
6: 0x10180fbc6 - make_test::closure.6451
7: 0x101810a8c - boxed::F.FnBox::call_box::h4518433956128595388
8: 0x10183b34f - boxed::F.FnBox::call_box::h17736871663463343674
9: 0x101838937 - rt::unwind::try::try_fn::h1582047561577903298
10: 0x10189cd28 - rust_try_inner
11: 0x10189cd15 - rust_try
12: 0x101838c1e - boxed::F.FnBox::call_box::h18004624870484171567
13: 0x10189975d - sys:🧵:Thread:🆕:thread_start::h5fcf8fe12ec3c274mYu
14: 0x7fff85a40771 - _pthread_start

failures:
hide_after_create.html == hide_after_create_ref.html

[Ms2ger]

@bors-servo: retry

• #5958

[bors-servo]

⌛ Testing commit 656a8ee with merge f4381a6...

[bors-servo]

☀️ Test successful - android, gonk, linux1, linux2, mac1, mac2