See flutter/flutter#110016 for context.

• code pinned to 2.9 for compatibility with legacy code:
  packages/devtools_app/assets/scripts/inspector_polyfill_script.dart:49:// @dart=2.9
• excluded files:
  packages/devtools_app/test/fixtures/flutter_app/lib/overflow_errors.dart:5:// @dart=2.9:
  Migrate case studies to null safety #4420
• convert case_study/memory_leak to null safety:
  Migrate case studies to null safety #4420
• convert case_study/code_size/optimized/code_size_images to null safety:
  Migrate case studies to null safety #4420
• convert case_study/code_size/optimized/code_size_package to null safety:
  Migrate case studies to null safety #4420
• convert case_study/code_size/unoptimized/code_size_images to null safety:
  Migrate case studies to null safety #4420
• convert case_study/code_size/unoptimized/code_size_package to null safety:
  Migrate case studies to null safety #4420
• convert case_study/platform_channel to null safety:
  Migrate case studies to null safety #4420
• convert packages/devtools_app/test/fixtures/flutter_app to null safety:
  Migrate case studies to null safety #4420