Preapproving dart2js and ddc NNBD failures for https://dart-review.googlesource.com/c/sdk/+/141252

[liamappelbe]

I fixed some strong mode tests in https://dart-review.googlesource.com/c/sdk/+/141252, but it seems to have broken some dart2js and ddc tests:
https://logs.chromium.org/logs/dart/buildbucket/cr-buildbucket.appspot.com/8884361847891432912/+/steps/test_results/0/logs/new_test_failures__logs_/0
https://logs.chromium.org/logs/dart/buildbucket/cr-buildbucket.appspot.com/8884361135081414064/+/steps/test_results/0/logs/new_test_failures__logs_/0

I think the fixes are legit, so it's possible that these tests also need to be updated for strong mode.

[srujzs]

For lib_2/html/element_test, it's relying on calling the List.length setter to throw an UnsupportedError => sdk_nnbd/lib/html/dart2js/html_dart2js.dart:11711 (GitHub isn't letting me view files this large so I can't directly link it). With the changes in that CL, it's never called. The proper fix is to probably implement insertAll in the class that extends ListBase and explicitly throw the error there.

[sigmundch]

The ddc failure on error_stack_trace2_test is because we don't try to map the browser's stack overflow error to Dart's overflow error. It's pretty low-pri for us to do so, so I'm inclined to adjust how the test checks for this.

I sent you a CL here: https://dart-review.googlesource.com/c/sdk/+/142200

And file a bug for DDC here: #41308

[srujzs]

lib_2/html/element_test should be passing now.

[sigmundch]

Thanks, error_stack_trace2_test is passing since 42ce378, so I think we can close this.