the dart2js platform files.
The main use-case right now is in compile-platform, but the way it is implemented
makes this available to any fasta tool.
This also adds resolveInputUri so we don't incorrectly treat supported URIs as file:* Uris.
Fixes https://github.com/dart-lang/sdk/issues/32633
Change-Id: I0ea3b1128352e72957b35823c6a1749ee418768b
Reviewed-on: https://dart-review.googlesource.com/56282
Reviewed-by: Zach Anderson <zra@google.com>
Reviewed-by: Peter von der Ahé <ahe@google.com>
Commit-Queue: Sigmund Cherem <sigmund@google.com>