Find and replace all "new " for ""

[GustavoContreiras]

Dart 2 makes the new keyword optional. Even in Dart 1, its meaning was never clear because factory constructors mean a new invocation may still not actually return a new object.

The language still permits new in order to make migration less painful, but consider it deprecated and remove it from your code.

https://dart-lang.github.io/linter/lints/unnecessary_new.html
https://www.dartlang.org/guides/language/effective-dart/usage#dont-use-new