implement historical srcElement attribute for Event interface

[drexler]

Implementation of srcElement attribute for Event interface. Reference: https://dom.spec.whatwg.org/#dom-event-srcelement

---

• ./mach build -d does not report any errors
• ./mach test-tidy does not report any errors
• These changes fix #22880 (GitHub issue number if applicable)

• There are tests for these changes

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This change is 

[highfive]

Thanks for the pull request, and welcome! The Servo team is excited to review your changes, and you should hear from @Manishearth (or someone else) soon.

[highfive]

Heads up! This PR modifies the following files:

• @asajeffrey: components/script/dom/event.rs, components/script/dom/webidls/Event.webidl
• @KiChjang: components/script/dom/event.rs, components/script/dom/webidls/Event.webidl

[highfive]

Warning

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

[Manishearth]

@bors-servo r+

[bors-servo]

📌 Commit dd731aa has been approved by Manishearth

[bors-servo]

⌛ Testing commit dd731aa with merge e88f9a5...

[Manishearth]

Thanks!

[bors-servo]

💔 Test failed - linux-rel-css

[CYBAI]

Need to update these test expectations!

{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "Event interface: attribute srcElement", 
    "test": "/dom/interfaces.html?exclude=Node", 
    "line": 89302, 
    "action": "test_result", 
    "expected": "FAIL"
}
{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "Event interface: document.createEvent(\"Event\") must inherit property \"srcElement\" with the proper type", 
    "test": "/dom/interfaces.html?exclude=Node", 
    "line": 89329, 
    "action": "test_result", 
    "expected": "FAIL"
}
{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "Event interface: new Event(\"foo\") must inherit property \"srcElement\" with the proper type", 
    "test": "/dom/interfaces.html?exclude=Node", 
    "line": 89354, 
    "action": "test_result", 
    "expected": "FAIL"
}
{
    "status": "PASS", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": "Event interface: new CustomEvent(\"foo\") must inherit property \"srcElement\" with the proper type", 
    "test": "/dom/interfaces.html?exclude=Node", 
    "line": 89390, 
    "action": "test_result", 
    "expected": "FAIL"
}

[drexler]

@Manishearth updated the test expectations for this PR. Sorry for multiple commits - still getting to grips with my first PR into Servo.

[Manishearth]

@bors-servo r+

[bors-servo]

📌 Commit 96bff3c has been approved by Manishearth

[bors-servo]

⌛ Testing commit fff8a09 with merge d364b28...

[bors-servo]

💔 Test failed - linux-rel-css

[jdm]

@bors-servo retry

• #13480

[bors-servo]

⌛ Testing commit fff8a09 with merge ee00aa0...

[bors-servo]

💔 Test failed - linux-rel-wpt

[jdm]

Need to update some more test results:

  ▶ Unexpected subtest result in /dom/events/Event-initEvent.html:
  └ PASS [expected FAIL] Properties of initEvent(type, true, true)

  ▶ Unexpected subtest result in /dom/events/Event-initEvent.html:
  └ PASS [expected FAIL] Properties of initEvent(type, true, false)

  ▶ Unexpected subtest result in /dom/events/Event-initEvent.html:
  └ PASS [expected FAIL] Properties of initEvent(type, false, true)

  ▶ Unexpected subtest result in /dom/events/Event-initEvent.html:
  └ PASS [expected FAIL] Properties of initEvent(type, false, false)

[drexler]

@jdm is there a command i can run locally to discover these failing tests?

[jdm]

@drexler I suggested that in my original issue comment in #22880 (comment) :)

[jdm]

@bors-servo r-

[bors-servo]

☔ The latest upstream changes (presumably #23465) made this pull request unmergeable. Please resolve the merge conflicts.

[jdm]

@drexler Are you planning to finish updating the test results?

[drexler]

@jdm ooops...totally slipped off my radar. I'll tackle it tonight and update the PR.

[jdm]

Closing due to inactivity.