[dart2js] Strengthen HBoolConversion in types_propagation
[dart2js] Strengthen HBoolConversion in types_propagation

Change-Id: I811cc43b21990eea79f97e65a7681661af0cef8e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/160344
Commit-Queue: Stephen Adams <60cb5b73b7e0cb7dcda53302da4fab6ecfc7fa8b@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