Puppeteer tests for the Dart Debug Extension are flaky on CI

[elliette]

[bkonyi]

Context: Puppeteer is the recommended way to test Chrome extensions.

We're using a Dart package to interact with Puppeteer. These tests are flaky, so @elliette has been running these manually (found under dwds/test/puppeteer/). They've never actually been run on CI, but it should be possible.