Compiler: Remove two unused fromDataSource constructors
Compiler: Remove two unused fromDataSource constructors

Change-Id: Id7096531e030e13ea0d8499244aff0ad59e3cecf
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/154821
Commit-Queue: Samuel Rawlins <5cf2cac5eec2ad6d0eb2b0f4ff6af9a590ce2bf6@google.com>
Reviewed-by: Sigmund Cherem <beaea8fd7d2a56555046ba4f362c8a93e3938576@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk