See https://github.com/whatwg/html/issues/2490 for discussion. https://github.com/whatwg/html/issues/2626 for the specification change. And https://github.com/w3c/web-platform-tests/issues/5776 for tests (url/failure.html).
Gecko and Edge already throw.
Created attachment 347463 [details] Patch
Attachment 347463 [details] did not pass style-queue: ERROR: Source/WebCore/page/DOMWindow.cpp:2238: Extra space before ( in function call [whitespace/parens] [4] Total errors found: 1 in 9 files If any of these errors are false positives, please file a bug against check-webkit-style.
Comment on attachment 347463 [details] Patch Looks fine. Idiom for returning nullptr in such cases is pretty ugly. For website programmers who did this by accident, it seems the exception is not as clear as the wording of the console message was.
Comment on attachment 347463 [details] Patch Attachment 347463 [details] did not pass win-ews (win): Output: https://webkit-queues.webkit.org/results/8912468 New failing tests: http/tests/security/contentSecurityPolicy/userAgentShadowDOM/allow-video.html
Created attachment 347477 [details] Archive of layout-test-results from ews201 for win-future The attached test failures were seen while running run-webkit-tests on the win-ews. Bot: ews201 Port: win-future Platform: CYGWIN_NT-6.1-2.9.0-0.318-5-3-x86_64-64bit
Created attachment 347490 [details] Patch
Comment on attachment 347490 [details] Patch Clearing flags on attachment: 347490 Committed r235050: <https://trac.webkit.org/changeset/235050>
All reviewed patches have been landed. Closing bug.
<rdar://problem/43534520>