Improved inferrer to handle some cases of JS-fragments.
The JS-fragment to copy the array caused the inferrer to be too
pessimistic about list-tracing into List.of.
Change-Id: I0cb4f7610d971d7927d973bd2b0b532d4cef9a7e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/173883
Commit-Queue: Stephen Adams <sra@google.com>
Reviewed-by: Mayank Patke <fishythefish@google.com>
Stephen Adams