Layout test imported/w3c/web-platform-tests/custom-elements/microtasks-and-constructors.html is flaky

• Component: New Bugs
• Status: NEW ---

[Matt Lewis]

The test imported/w3c/web-platform-tests/custom-elements/microtasks-and-constructors.html is flaky.

It was added in the revision https://trac.webkit.org/changeset/217225/webkit
On the flakiness dashboard, the test has failed on Sierra Leaks, Sierra Debug WK1, Sierra and El Capitan Release WK2, and iOS Sim WK2. 

https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=imported%2Fw3c%2Fweb-platform-tests%2Fcustom-elements%2Fmicrotasks-and-constructors.html

https://build.webkit.org/results/Apple%20Sierra%20Release%20WK2%20(Tests)/r217568%20(1849)/results.html
https://build.webkit.org/builders/Apple%20Sierra%20Release%20WK2%20(Tests)/builds/1849

diff:
--- /Volumes/Data/slave/sierra-release-tests-wk2/build/layout-test-results/imported/w3c/web-platform-tests/custom-elements/microtasks-and-constructors-expected.txt
+++ /Volumes/Data/slave/sierra-release-tests-wk2/build/layout-test-results/imported/w3c/web-platform-tests/custom-elements/microtasks-and-constructors-actual.txt
@@ -2,6 +2,6 @@
 PASS Microtasks evaluate immediately when the stack is empty inside the parser 
 FAIL Microtasks evaluate immediately when the stack is empty inside the parser, causing the checks on no attributes to fail assert_false: The attribute must not be present expected false got true
 PASS Microtasks evaluate afterward when the stack is not empty using createElement() 
-PASS Microtasks evaluate afterward when the stack is not empty using the constructor 
+FAIL Microtasks evaluate afterward when the stack is not empty using the constructor assert_array_equals: lengths differ, expected 3 got 2
 PASS Microtasks evaluate afterward when the stack is not empty due to upgrades