[co19] Roll co19 to e3d6ccfe8fa278041316f7dc958fdd8c2b447b6c
[co19] Roll co19 to e3d6ccfe8fa278041316f7dc958fdd8c2b447b6c

2020-08-03 sgrekhov@unipro.ru LibTest/core tests fixed after tryjob attempt
2020-08-03 irina.arkhipets@gmail.com Fixes 879: LibTest\typed_data\Float64x2 tests adopted for null safety.
2020-08-03 irina.arkhipets@gmail.com Fixes 878: LibTest\typed_data\Float64List tests adopted for null safety.

Change-Id: I12e86b1b3a8972797264f9142b0601ff44ccdcc3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/156886
Reviewed-by: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@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