CP-3228 Use test runner when collecting coverage

[greglittlefield-wf]

When running tests coverage, platform selectors don't work as expected since the test runner isn't being used.

E.g., tests with testOn: !content-shell still run during coverage.

Now that dart-lang/test#36 isn't blocked, this should be possible.

[evanweible-wf]

Awesome! Thanks for the heads up @greglittlefield-wf. I'll try to roll this in to V2 with the rewrite of the coverage task.

[greglittlefield-wf]

This also prevents us from using test tags, which seem to be the most promising way so far to run certain tests conditionally based on whether you're in the DDC: dart-lang/test#652

[maxwellpeterson-wf]

@greglittlefield-wf could you clarify this part: Now that dart-lang/test#36 isn't blocked, this should be possible.

@evanweible-wf

[greglittlefield-wf]

@maxwellpeterson-wf I think when I created this issue, it seemed possible to be able to hook coverage and the test runner together with some observatory/isolate magic.

However, based on this comment in that issue I linked: dart-lang/test#36 (comment)

I agree that the best approach here is for test to be involved in coverage collecting—that's the best way to ensure a smooth user interface and to avoid dependencies on test's internal structure, which is not a guaranteed stable interface.

it seems like it's probably best to rely on changes in test to facilitate coverage collection.

[evanweible-wf]

Coverage collection through the test runner is in progress, so this should no longer need to be a ddev concern.