Add Dart 2.0 migration stubs to packages that implement Stream, StreamTransformer, and Converter

[keertip]

To help with the migration and changes to the core libs, stubs will be added to a number of core packages that implement these interfaces to ensure that these packages remain unbroken during the transition. These migration stubs can be replaced by full implementations at any time.

Stub template here: https://gist.github.com/lrhn/b99fe5f73a10b3b1a91579853056d08b .

Packages to be updated:

• _discoveryapis_commons
  • PR: Updates for Dart 2.0 core library changes (wave 2.2) dart-archive/discoveryapis_commons#11
  • Roll internal
• async
  • Initial update: Updates for Dart 2.0 core library changes (wave 2.2) dart-archive/async#45
  • Roll Deps
  • Roll internal
  • Clean up interim APIs: Update implementations of Stream.{lastWhere, firstWhere} for Dart 2 core#311
    • Deprecate DelegatingStream.typed and make it delegate to Stream.cast dart-archive/async#54
• bazel_worker
• grpc
• http2
• http_server
  • PR: Updates for Dart 2.0 core library changes (wave 2.2) dart-archive/http_server#39
  • Roll internal
• mime
  • PR: Updates for Dart 2.0 core library changes (wave 2.2) dart-archive/mime#16
  • Roll deps
  • Roll internal
• shuttlecock
  • First PR here: Updates for Dart 2.0 core library changes (wave 2.2) - step 1 alexeieleusis/shuttlecock#41
  • Roll internal
  • Second PR is prepared in a branch: https://github.com/leafpetersen/shuttlecock/tree/corelib_2_2_2
  • Roll internal
• stream_transform
  • PR: Updates for Dart 2.0 core library changes (wave 2.2) stream_transform#42
    • published as 0.0.10
  • Roll internal
• testing
  • https://dart-review.googlesource.com/37864
• utf
  • PR: Updates for Dart 2.0 core library changes (wave 2.2) dart-archive/utf#6
  • Roll deps
  • Roll internal
• vm_service_client
  • PR: Updates for Dart 2.0 core library changes (wave 2.2) dart-archive/vm_service_client#24
  • Roll internal
• watcher
  • PR: Updates for Dart 2.0 corelib changes (wave 2.2). watcher#47
  • Roll deps
  • Roll internal
• web_socket_channel
  • PR: Updates for Dart 2.0 corelib changes (wave 2.2). web_socket_channel#11
  • Roll deps
  • Roll internal

[keertip]

cc @anders-sandholm @lrhn @matanlurey @grouma @srawlins

[leafpetersen]

cc @lrhn @anders-sandholm @keertip @grouma @matanlurey @srawlins @vsmenon @dgrove @kevmoo

[leafpetersen]

Closing this, since the API changes are all done. If we need package updates for uses of defaultValue, I'll file a separate issue.