Make IterableMixinWorkaround using classes return correctly typed Iterables.

Make IterableMixinWorkaround using classes return correctly typed Iterables.

BUG= http://dartbug.com/13646
R=floitsch@google.com

Committed: https://code.google.com/p/dart/source/detail?r=38372

[floitsch, 2014-07-17 11:39:21]

LGTM after verification that this doesn't introduce big performance and/or size
regressions.

https://codereview.chromium.org/397243002/diff/1/sdk/lib/internal/iterable.dart
File sdk/lib/internal/iterable.dart (right):

https://codereview.chromium.org/397243002/diff/1/sdk/lib/internal/iterable.da...
sdk/lib/internal/iterable.dart:283: return new SubListIterable<E>(_iterable,
_start + count, _endOrLength);
newStart

[floitsch, 2014-07-17 11:39:55]

Also, I think this warrants a "Be careful" mail to the mailing-list.
This bug-fix could potentially break programs that relied on the wrong behavior.

[Lasse Reichstein Nielsen, 2014-07-18 07:47:42]

Performance looks fine. I'll write a mail, but since it was only broken on the
VM, code that worked with dart2js shouldn't be affected.

[Lasse Reichstein Nielsen, 2014-07-18 08:08:28]

Committed patchset #2 manually as r38372 (presubmit successful).