Test failures on [dart2wasm] language/regress/regress21795_test

[jyameo]

There are new test failures on [dart2wasm] Fix param info lookup to match signature lookup logic....Elements. Write more ElementImpl as references, not as fragments..

The tests

language/regress/regress21795_test RuntimeError (expected Pass)

are failing on configurations

dart2wasm-linux-optimized-jsc

Logs: https://dart-ci.appspot.com/log/dart2wasm-linux-optimized-jsc/dart2wasm-linux-optimized-jsc/2600/language/regress/regress21795_test