Fix static typing problem in analysis_server tests.

Fix static typing problem in analysis_server tests.

After changing argument of `Future` constructor to be `()->FutureOr<T>`,
the `()->Future<dynamic>` argument didn't work.
Problem compounded by return type of `Stream<T>.firstWhere` being `dynamic`.

R=karlklose@google.com

Committed: https://github.com/dart-lang/sdk/commit/83298690b00680a15dc37ccdd4e1fdd79d4c9c33

[Lasse Reichstein Nielsen, 2017-03-31 12:02:10]

lrn@google.com changed reviewers:
+ karlklose@google.com

[karlklose, 2017-03-31 12:05:15]

LGTM

[Lasse Reichstein Nielsen, 2017-03-31 12:12:37]

Description was changed from

==========
Fix static typing problem in analysis_server tests.

After changing argument of `Future` constructor to be `()->FutureOr<T>`,
the `()->Future<dynamic>` argument didn't work.
Problem compounded by return type of `Stream<T>.firstWhere` being `dynamic`.
==========

to

==========
Fix static typing problem in analysis_server tests.

After changing argument of `Future` constructor to be `()->FutureOr<T>`,
the `()->Future<dynamic>` argument didn't work.
Problem compounded by return type of `Stream<T>.firstWhere` being `dynamic`.

R=karlklose@google.com

Committed:
https://github.com/dart-lang/sdk/commit/83298690b00680a15dc37ccdd4e1fdd79d4c9c33
==========

[Lasse Reichstein Nielsen, 2017-03-31 12:12:38]

Committed patchset #1 (id:1) manually as
83298690b00680a15dc37ccdd4e1fdd79d4c9c33 (presubmit successful).

[Brian Wilkerson, 2017-03-31 13:41:32]

brianwilkerson@google.com changed reviewers:
+ brianwilkerson@google.com

[Brian Wilkerson, 2017-03-31 13:41:33]

lgtm