Make await for cancel the stream when breaking out of the loop

Make await for cancel the stream when breaking out of the loop

Wrap the await-for loop in a try-finally statement that ensures that
the stream is cancelled. Also adding the ability to the
AsyncStartStreamController class to return a cancellation future.

The cancel() call at the end of the await-for loop is not awaiting
the cancellation future yet. This is not part of the spec at this
point.

R=regis@google.com

Committed: https://code.google.com/p/dart/source/detail?r=44689

[hausner, 2015-03-24 23:18:34]

hausner@google.com changed reviewers:
+ lrn@chromium.org, regis@google.com

[regis, 2015-03-24 23:46:27]

LGTM with comments

https://codereview.chromium.org/1014273003/diff/1/runtime/lib/core_patch.dart
File runtime/lib/core_patch.dart (right):

https://codereview.chromium.org/1014273003/diff/1/runtime/lib/core_patch.dart...
runtime/lib/core_patch.dart:97: if ((cancellationCompleter != null &&
Redundant pair of parenthesis

https://codereview.chromium.org/1014273003/diff/1/runtime/lib/core_patch.dart...
runtime/lib/core_patch.dart:114: if ((cancellationCompleter != null) &&
ditto

https://codereview.chromium.org/1014273003/diff/1/runtime/vm/parser.cc
File runtime/vm/parser.cc (right):

https://codereview.chromium.org/1014273003/diff/1/runtime/vm/parser.cc#newcod...
runtime/vm/parser.cc:8489: 
remove extra blank line

https://codereview.chromium.org/1014273003/diff/1/runtime/vm/parser.cc#newcod...
runtime/vm/parser.cc:8498: // current exception.
The code may not access captured variables, but if you set a breakpoint in the
debugger to inspect these variables, you will need a valid current context.

https://codereview.chromium.org/1014273003/diff/1/runtime/vm/parser.cc#newcod...
runtime/vm/parser.cc:8503: // We don't need to copy the current execption and
stack trace variables
typo

[hausner, 2015-03-24 23:57:29]

Thanks Regis. Comments addressed.

I'll wait for Lasse's feedback and check in tomorrow morning.

https://codereview.chromium.org/1014273003/diff/1/runtime/lib/core_patch.dart
File runtime/lib/core_patch.dart (right):

https://codereview.chromium.org/1014273003/diff/1/runtime/lib/core_patch.dart...
runtime/lib/core_patch.dart:97: if ((cancellationCompleter != null &&
On 2015/03/24 23:46:27, regis wrote:
> Redundant pair of parenthesis

Done.

https://codereview.chromium.org/1014273003/diff/1/runtime/lib/core_patch.dart...
runtime/lib/core_patch.dart:114: if ((cancellationCompleter != null) &&
On 2015/03/24 23:46:27, regis wrote:
> ditto

This one actually had the closing paren in the right place. Technically
redundant but I think our coding standards want a set of parens around the
(in)equality test.

https://codereview.chromium.org/1014273003/diff/1/runtime/vm/parser.cc
File runtime/vm/parser.cc (right):

https://codereview.chromium.org/1014273003/diff/1/runtime/vm/parser.cc#newcod...
runtime/vm/parser.cc:8489: 
On 2015/03/24 23:46:27, regis wrote:
> remove extra blank line

Done.

https://codereview.chromium.org/1014273003/diff/1/runtime/vm/parser.cc#newcod...
runtime/vm/parser.cc:8498: // current exception.
On 2015/03/24 23:46:27, regis wrote:
> The code may not access captured variables, but if you set a breakpoint in the
> debugger to inspect these variables, you will need a valid current context.

True, thank you. Removed comment.

https://codereview.chromium.org/1014273003/diff/1/runtime/vm/parser.cc#newcod...
runtime/vm/parser.cc:8503: // We don't need to copy the current execption and
stack trace variables
On 2015/03/24 23:46:27, regis wrote:
> typo

Done.

[hausner, 2015-03-25 17:41:48]

Committed patchset #2 (id:20001) manually as r44689 (presubmit successful).

[hausner, 2015-03-25 17:43:11]

If Lasse has any comments, I'll address them in a later CL.