This flag is unused and the behavior it enables was only useful along with
`dart:mirrors`.
- Remove the flag and the field on the options object.
- Prune code branches that are no longer reachable.
- Remove or inline some functions that became either empty or trivially small.
- Remove the manual check for a `dart:mirrors` import since this is handled by
the CFE now.
- Remove references to the flag in tests.
- Remove test files which only existed to enable the flag for other tests.
Change-Id: I21bf594271fb4eeb5b73fcbf07da736e9e8d1f33
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/138018
Reviewed-by: Nicholas Shahan <nshahan@google.com>
Commit-Queue: Nate Bosch <nbosch@google.com>
Auto-Submit: Nate Bosch <nbosch@google.com>
Nate Bosch
9d76737487