Treat indefinite percentages as auto for margin collapse

[Loirooriol]

The top and bottom margins of an element can collapse through if its height is auto or zero. Indefinite percentages behave as auto, so they shouldn't prevent the margins from collapsing.

---

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

• There are tests for these changes OR
• These changes do not require tests because ___

[github-actions]

🔨 Triggering try run (#8651561510) for Linux WPT

[github-actions]

Test results for linux-wpt-layout-2020 from try job (#8651561510):

Flaky unexpected result (19)

• TIMEOUT [expected OK] /_webgl/conformance/glsl/misc/shader-uniform-packing-restrictions.html (#28103)
• OK /css/css-fonts/variations/at-font-face-font-matching.html (#20684)
  • PASS [expected FAIL] subtest: Matching font-weight: '400' should prefer '450 460' over '500'
  • PASS [expected FAIL] subtest: Matching font-weight: '500' should prefer '500' over '450 460'
  • PASS [expected FAIL] subtest: Matching font-weight: '500' should prefer '501 550' over '502 560'
  • PASS [expected FAIL] subtest: Matching font-stretch: '110%' should prefer '110% 120%' over '115% 116%'
  • PASS [expected FAIL] subtest: Matching font-style: 'italic' should prefer 'oblique 0deg' over 'oblique -60deg -30deg'
  • PASS [expected FAIL] subtest: Matching font-style: 'oblique 20deg' should prefer 'oblique 10deg' over 'italic'
  • PASS [expected FAIL] subtest: Matching font-style: 'oblique 0deg' should prefer 'oblique 0deg' over 'oblique 5deg'
• PASS [expected FAIL] /css/css-sizing/dynamic-available-size-iframe.html (#31559)
• TIMEOUT [expected OK] /dom/events/webkit-transition-end-event.html (#26497)
  • TIMEOUT [expected PASS] subtest: webkitTransitionEnd event listener should not trigger if an unprefixed listener also exists

    Test timed out
    

  • NOTRUN [expected PASS] subtest: webkitTransitionEnd event listener should not trigger if an unprefixed event handler also exists
  • NOTRUN [expected FAIL] subtest: event types for prefixed and unprefixed transitionend event listeners should be named appropriately
  • NOTRUN [expected PASS] subtest: webkitTransitionEnd event listener is case sensitive
• TIMEOUT /fetch/api/basic/keepalive.any.html (#29536)
  • TIMEOUT [expected PASS] subtest: [keepalive] simple GET request on 'load' [no payload]; setting up

    Test timed out
    

  • NOTRUN [expected TIMEOUT] subtest: [keepalive] simple GET request on 'pagehide' [no payload]; setting up
• TIMEOUT [expected OK] /fetch/api/redirect/redirect-keepalive.https.any.html
  • TIMEOUT [expected PASS] subtest: [keepalive][iframe][load] mixed content redirect; setting up

    Test timed out
    

• OK /fetch/private-network-access/worker-blob-fetch.tentative.window.html (#30064)
  • PASS [expected FAIL] subtest: local to local: success.
• OK /html/browsers/browsing-the-web/navigating-across-documents/initial-empty-document/load-pageshow-events-window-open.html (#28691)
  • PASS [expected FAIL] subtest: load event does not fire on window.open('about:blank')
• OK /html/browsers/browsing-the-web/navigating-across-documents/navigation-unload-cross-origin.sub.window.html (#29056)
  • FAIL [expected PASS] subtest: Cross-origin navigation started from unload handler must be ignored

    promise_test: Unhandled rejection with value: object "SecurityError: The operation is insecure."
    

• OK /html/browsers/browsing-the-web/navigating-across-documents/navigation-unload-same-origin.window.html (#29049)
  • PASS [expected FAIL] subtest: Same-origin navigation started from unload handler must be ignored
• OK /html/browsers/history/the-history-interface/traverse_the_history_4.html (#21383)
  • FAIL [expected PASS] subtest: Multiple history traversals, last would be aborted

    assert_array_equals: Pages opened during history navigation expected property 1 to be 5 but got 3 (expected array [6, 5] got [6, 3])
    

• OK /html/browsers/history/the-history-interface/traverse_the_history_5.html (#21383)
  • FAIL [expected PASS] subtest: Multiple history traversals, last would be aborted

    assert_array_equals: Pages opened during history navigation expected property 1 to be 5 but got 3 (expected array [6, 5] got [6, 3])
    

• TIMEOUT [expected OK] /html/browsers/history/the-history-interface/traverse_the_history_write_onload_1.html (#21581)
  • TIMEOUT [expected PASS] subtest: Traverse the history when a history entry is written in the load event

    Test timed out
    

• TIMEOUT [expected OK] /html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_nonescaping-3.html (#24066)
  • NOTRUN [expected FAIL] subtest: Check that popups from a sandboxed iframe do not escape the sandbox
• OK /html/semantics/embedded-content/the-img-element/non-active-document.html (#21544)
  • FAIL [expected PASS] subtest: DOMParser

    assert_unreached: got unexpected load event Reached unreachable code
    

  • FAIL [expected PASS] subtest: createHTMLDocument

    assert_unreached: got unexpected error event Reached unreachable code
    

  • FAIL [expected PASS] subtest: <template>

    assert_unreached: got unexpected error event Reached unreachable code
    

• TIMEOUT /html/webappapis/scripting/events/compile-event-handler-settings-objects.html (#24246)
  • TIMEOUT [expected FAIL] subtest: The entry settings object while executing the compiled callback via Web IDL's invoke must be that of the node document

    Test timed out
    

• TIMEOUT /resource-timing/test_resource_timing.https.html (#25216)
  • PASS [expected FAIL] subtest: PerformanceEntry has correct name, initiatorType, startTime, and duration (img)
• TIMEOUT [expected OK] /webmessaging/with-ports/017.html (#24486)
  • TIMEOUT [expected PASS] subtest: origin of the script that invoked the method, about:blank

    Test timed out
    

• OK [expected TIMEOUT] /webmessaging/with-ports/018.html (#24485)
  • PASS [expected TIMEOUT] subtest: origin of the script that invoked the method, javascript:

Stable unexpected results that are known to be intermittent (9)

• TIMEOUT [expected OK] /html/infrastructure/urls/base-url/document-base-url-window-initiator-is-not-opener.https.window.html (#30970)
• OK /html/interaction/focus/the-autofocus-attribute/document-with-fragment-valid.html (#28259)
  • PASS [expected FAIL] subtest: Autofocus elements in top-level browsing context's documents with URL fragments should be skipped.
• OK [expected CRASH] /html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_escaping-1.html (#22647)
  • FAIL [expected TIMEOUT] subtest: Check that popups from a sandboxed iframe escape the sandbox if allow-popups-to-escape-sandbox is used

    assert_equals: It came from a sandboxed iframe expected "null" but got "http://web-platform.test:8000"
    

• TIMEOUT [expected CRASH] /html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_escaping-2.html (#22667)
• CRASH [expected TIMEOUT] /html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_escaping-3.html (#24057)
• TIMEOUT [expected OK] /html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_nonescaping-1.html (#24066)
  • NOTRUN [expected FAIL] subtest: Check that popups from a sandboxed iframe do not escape the sandbox
• OK /html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_nonescaping-2.html (#22154)
  • FAIL [expected NOTRUN] subtest: Check that popups from a sandboxed iframe do not escape the sandbox

    assert_equals: It came from a sandboxed iframe expected "null" but got "http://web-platform.test:8000"
    

• OK [expected TIMEOUT] /resource-timing/nested-context-navigations-iframe.html (#24311)
  • PASS [expected NOTRUN] subtest: Test that iframe navigations are not observable by the parent
  • PASS [expected NOTRUN] subtest: Test that crossorigin iframe navigations are not observable by the parent
  • PASS [expected NOTRUN] subtest: Test that cross-site iframe navigations are not observable by the parent
  • PASS [expected NOTRUN] subtest: Test that iframe refreshes are not observable by the parent
  • PASS [expected NOTRUN] subtest: Test that crossorigin iframe refreshes are not observable by the parent
  • PASS [expected NOTRUN] subtest: Test that cross-site iframe refreshes are not observable by the parent
• OK /workers/WorkerGlobalScope-close.html (#23064)
  • PASS [expected FAIL] subtest: Test sending a message after closing.

Stable unexpected results (1)

• PASS [expected FAIL] /css/CSS2/normal-flow/margin-collapse-through-percentage-height-block.html

[github-actions]

⚠️ Try run (#8651561510) failed.