Support both older and newer implementations of dart:async.

Support both older and newer implementations of dart:async.

The VM target's continuation transformer uses a class that was originally
named _StreamIteratorImpl and then renamed to _StreamIterator.  If looking
up the old name fails, try the new name.

BUG=
R=jensj@google.com

Committed: https://github.com/dart-lang/kernel/commit/480abf7604fd64b96bd4b974352db034179f413a

[Kevin Millikin (Google), 2016-11-02 08:14:53]

kmillikin@google.com changed reviewers:
+ jensj@google.com

[jensj, 2016-11-02 08:22:43]

lgtm, though it might seem reasonable to look for the new name first and then
fallback to the old name instead of the other way around.

[Kevin Millikin (Google), 2016-11-02 08:32:31]

Description was changed from

==========
Support both older and newer implementations of dart:async.

The VM target's continuation transformer uses a class that was originally
named _StreamIteratorImpl and then renamed to _StreamIterator.  If looking
up the old name fails, try the new name.

BUG=
==========

to

==========
Support both older and newer implementations of dart:async.

The VM target's continuation transformer uses a class that was originally
named _StreamIteratorImpl and then renamed to _StreamIterator.  If looking
up the old name fails, try the new name.

BUG=
R=jensj@google.com

Committed:
https://github.com/dart-lang/kernel/commit/480abf7604fd64b96bd4b974352db03417...
==========

[Kevin Millikin (Google), 2016-11-02 08:32:37]

Committed patchset #1 (id:1) manually as
480abf7604fd64b96bd4b974352db034179f413a (presubmit successful).