Fix "continue to a label" in dart2js async code.

Fix "continue to a label" in dart2js async code.

Actually there were two independent problems

1: continue would jump to the starting point of the label, instead of
the continue-point of the labelled loop.

2: A for-initializer with no awaits in the for would still get its
variables hoisted, so

    label: for(var i = 1; i < 10; i++) {continue label};

would transform to:

    label: {
      i = 1
      for(; i < 10; i++) {continue label;}
    }

And that fails.


BUG=
R=floitsch@google.com

Committed: https://code.google.com/p/dart/source/detail?r=44499

[sigurdm, 2015-03-13 14:05:57]

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

[floitsch, 2015-03-13 14:20:23]

LGTM.

https://codereview.chromium.org/1003213002/diff/20001/pkg/compiler/lib/src/js...
File pkg/compiler/lib/src/js/rewrite_async.dart (right):

https://codereview.chromium.org/1003213002/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js/rewrite_async.dart:1502: return initializations.isEmpty
? js.number(0)
Make this an if.
Explain why "0".

[sigurdm, 2015-03-16 08:43:52]

https://codereview.chromium.org/1003213002/diff/20001/pkg/compiler/lib/src/js...
File pkg/compiler/lib/src/js/rewrite_async.dart (right):

https://codereview.chromium.org/1003213002/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js/rewrite_async.dart:1502: return initializations.isEmpty
? js.number(0)
On 2015/03/13 14:20:22, floitsch wrote:
> Make this an if.
> Explain why "0".

Done.

[sigurdm, 2015-03-16 08:45:55]

Committed patchset #3 (id:40001) manually as 44499 (presubmit successful).