Failures on [co19] Roll co19 to 74eec903ea06fa09dc8799b0552d55b581a82996

[whesse]

There are new test failures on [co19] Roll co19 to 74eec903ea06fa09dc8799b0552d55b581a82996.

This rolls in the change dart-lang/co19@7e99f4e
in co19, which marks some tests as having compile-time errors on analyzer and cfe.
These errors aren't showing up as errors on cfe, but they are on analyzer.

The tests

co19/Language/Classes/Instance_Methods/Operators/return_type_t01 MissingCompileTimeError (expected Pass)
co19/Language/Classes/Setters/return_type_not_void_t01 MissingCompileTimeError (expected Pass)
co19/Language/Classes/Setters/syntax_t04 MissingCompileTimeError (expected Pass)
co19/Language/Classes/Setters/syntax_t05 MissingCompileTimeError (expected Pass)

are failing on configurations

cfe-strong-linux
cfe-weak-linux

@johnniwinther