Fix the old-hijack test.

Fix the old-hijack test.

We were testing for `is ZoneUnaryCallback` on a function returned by
expectAsync(). It turns out the expectAsync() wrappers make all
arguments optional, so `is ZoneUnaryCallback` returns true even if the
original function took two arguments. So instead, we test for
`is! ZoneBinaryCallback`.

R=kevmoo@google.com

Committed: https://github.com/dart-lang/shelf/commit/60e3f7fbfcc30ddb53b45cd0dc13361d38d1cdbc

[kevmoo, 2016-01-28 19:59:53]

lgtm

[nweiz, 2016-01-28 20:00:19]

Description was changed from

==========
Fix the old-hijack test.

We were testing for `is ZoneUnaryCallback` on a function returned by
expectAsync(). It turns out the expectAsync() wrappers make all
arguments optional, so `is ZoneUnaryCallback` returns true even if the
original function took two arguments. So instead, we test for
`is! ZoneBinaryCallback`.

R=kevmoo@google.com
==========

to

==========
Fix the old-hijack test.

We were testing for `is ZoneUnaryCallback` on a function returned by
expectAsync(). It turns out the expectAsync() wrappers make all
arguments optional, so `is ZoneUnaryCallback` returns true even if the
original function took two arguments. So instead, we test for
`is! ZoneBinaryCallback`.

R=kevmoo@google.com

Committed:
https://github.com/dart-lang/shelf/commit/60e3f7fbfcc30ddb53b45cd0dc13361d38d...
==========

[nweiz, 2016-01-28 20:00:20]

Committed patchset #1 (id:1) manually as
60e3f7fbfcc30ddb53b45cd0dc13361d38d1cdbc (presubmit successful).