How to add a simple Flutter device lab drive perf test

Do the following to add a blah perf test to the Flutter device lab:

1. Modify dev/devicelab/manifest.yaml to add a new entry blah

   • Always mark the new test to be flaky

2. Create your test file dev/devicelab/bin/tasks/blah.dart

   • Write a main function in blah.dart that runs a task using something like await task(createBlahPerfTest()). See https://github.com/flutter/flutter/blob/master/dev/devicelab/bin/tasks/cull_opacity_perf__timeline_summary.dart for a full example.

3. In dev/devicelab/lib/tasks/perf_tests.dart, add a new function createBlahPerfTest

   • Specify the path, drive test file, and the output name. There are many examples to follow in dev/devicelab/lib/tasks/perf_tests.dart
   • The meat of the test is usually in the drvier test file. See, for example, https://github.com/flutter/flutter/blob/master/dev/benchmarks/macrobenchmarks/test_driver/cull_opacity_perf_test.dart and https://github.com/flutter/flutter/blob/master/dev/benchmarks/complex_layout/test_driver/scroll_perf_test.dart

To test the device lab test blah locally, run

cd dev/devicelab
dart bin/run.dart -t blah

Alternatively, you can also run the drive test locally. For example:

cd dev/benchmarks/macrobenchmarks && flutter drive --profile test_driver/cull_opacity_perf.dart

or

cd dev/benchmarks/complex_layout && flutter drive --profile test_driver/scroll_perf.dart