Fix problems with async* and await for in dart2js.

Fix problems with async* and await for in dart2js.

The ssa backend would generate incorrect code for await for.

Async* finalizers would not be run when a paused stream is canceled.

BUG=
R=floitsch@google.com

Committed: https://code.google.com/p/dart/source/detail?r=44503

[sigurdm, 2015-03-16 13:13:41]

sigurdm@google.com changed reviewers:
+ floitsch@google.com

[floitsch, 2015-03-16 13:33:50]

LGTM.

https://codereview.chromium.org/1012623003/diff/1/pkg/compiler/lib/src/ssa/bu...
File pkg/compiler/lib/src/ssa/builder.dart (right):

https://codereview.chromium.org/1012623003/diff/1/pkg/compiler/lib/src/ssa/bu...
pkg/compiler/lib/src/ssa/builder.dart:6103: localsHandler = savedLocals;
I'm not 100% sure that one is correct (even in the original code).
It probably doesn't matter, because we box all try-variables, but it feels
wrong.

Copy over the comment from the original visitTry.

Maybe add a TODO: "we can probably do this, because try-variables are boxed.
Need to verify". or something similar.

[sigurdm, 2015-03-16 14:08:09]

https://codereview.chromium.org/1012623003/diff/1/pkg/compiler/lib/src/ssa/bu...
File pkg/compiler/lib/src/ssa/builder.dart (right):

https://codereview.chromium.org/1012623003/diff/1/pkg/compiler/lib/src/ssa/bu...
pkg/compiler/lib/src/ssa/builder.dart:6103: localsHandler = savedLocals;
On 2015/03/16 13:33:50, floitsch wrote:
> I'm not 100% sure that one is correct (even in the original code).
> It probably doesn't matter, because we box all try-variables, but it feels
> wrong.
> 
> Copy over the comment from the original visitTry.
> 
> Maybe add a TODO: "we can probably do this, because try-variables are boxed.
> Need to verify". or something similar.

Done.

[sigurdm, 2015-03-16 14:11:07]

Committed patchset #2 (id:20001) manually as 44503 (presubmit successful).