Remove tree-shaker as we're not using it, and it creates problems
when the SDK changes.
Remove scopes from AstBuilder as we will be phasing out AstBuilder
in favor of using BodyBuilder and the Forest API.
Change-Id: I51950c5d8bfb0493587336325f9da8f5bf8ecea6
Reviewed-on: https://dart-review.googlesource.com/57261
Commit-Queue: Peter von der Ahé <ahe@google.com>
Reviewed-by: Dan Rubel <danrubel@google.com>