CPLAT-7492 Run Dart 2 unit tests on dart2s and ddc

[todbachman-wf]

Motivation

When run in the browser in production, this code is compiled using dart2js. Let's run the unit tests on dart2js too in order to give us more confidence.

Changes

Updated travis configuration to run tests on the VM, DDC, and Dart2Js.

Release Notes

Run unit tests on the VM, DDC, and Dart2Js for Dart 2.

Review

See CONTRIBUTING.md for more details on review types (+1 / QA +1 / +10) and code review process.

Please review:

QA Checklist

• [ ] Tests were updated and provide good coverage of the changeset and other affected code
• [ ] Manual testing was performed if needed
  • [ ] Steps from PR author:
  • [ ] Anything falling under manual testing criteria outlined in CONTRIBUTING.md

Merge Checklist

While we perform many automated checks before auto-merging, some manual checks are needed:

• [ ] A Client Platform member has reviewed these changes
• [ ] There are no unaddressed comments - this check can be automated if reviewers use the "Request Changes" feature
• [ ] For release PRs - Version metadata in Rosie comment is correct

[aviary-wf]

Security Insights

No security relevant content was detected by automated scans.

Action Items

• Review PR for security impact; comment "security review required" if needed or unsure

• Verify aviary.yaml coverage of security relevant code

  Questions or Comments? Reach out on Slack: #support-infosec.

[olesiathoms-wk]

QA+1 CI passes

[todbachman-wf]

@Workiva/release-management-pp