Add Pool.close().

Add Pool.close().

R=rnystrom@google.com

Committed: https://github.com/dart-lang/pool/commit/30410bf531796a7ffdef64fd7953df7b6354bb3b

[Bob Nystrom, 2015-10-09 00:25:25]

lgtm

https://codereview.chromium.org/1393193004/diff/20001/lib/pool.dart
File lib/pool.dart (right):

https://codereview.chromium.org/1393193004/diff/20001/lib/pool.dart#newcode109
lib/pool.dart:109: return request().then((resource) {
Use async/await?

https://codereview.chromium.org/1393193004/diff/20001/lib/pool.dart#newcode124
lib/pool.dart:124: if (_closeGroup != null) return _closeGroup.future;
Document that it can be called more than once.

[nweiz, 2015-10-09 00:46:14]

Code review changes

[nweiz, 2015-10-09 00:46:20]

https://codereview.chromium.org/1393193004/diff/20001/lib/pool.dart
File lib/pool.dart (right):

https://codereview.chromium.org/1393193004/diff/20001/lib/pool.dart#newcode109
lib/pool.dart:109: return request().then((resource) {
On 2015/10/09 00:25:25, Bob Nystrom wrote:
> Use async/await?

This is used in test, which means we have to work around
https://github.com/dart-lang/sdk/issues/23497. I'll add a TODO.

https://codereview.chromium.org/1393193004/diff/20001/lib/pool.dart#newcode124
lib/pool.dart:124: if (_closeGroup != null) return _closeGroup.future;
On 2015/10/09 00:25:25, Bob Nystrom wrote:
> Document that it can be called more than once.

Done.

[nweiz, 2015-10-09 00:46:32]

Committed patchset #3 (id:40001) manually as
30410bf531796a7ffdef64fd7953df7b6354bb3b (presubmit successful).