Expect annotations

[Florian Loitsch]

I think I forgot to send a mail to the dart2js-devs...

We have recently added the following annotations to the expect-package (used in tests):

NoInline

AssumeDynamic

TrustTypeAnnotations

Example usage:

    @NoInline()

    @AssumeDynamic()

    confuse(x) => x;

We can now stop using hacks like the "double-return" or "new DateTime.now()", and make our intentions more explicit.

Please update old tests if you see these hacks.

Thanks.