allow null to be returned from the Chrome sourceUriProvider (dart-lang/coverage#333)

This was an incorrect migration originally it looks like, the test package returns null in a few different cases and it was previously handled a bit weirdly (adding entries with a null key). Now these are explicitly skipped.
3 files changed
tree: 92045b129b3a660a695d030cfae3e27eea5aaa35
  1. pkgs/