improve fasta unterminated string recovery

improve fasta unterminated string recovery

* enhance handling of unterminated strings
* update ast builder and string validator to handle unterminated strings

Committed: https://github.com/dart-lang/sdk/commit/6907345fb9323203a5cf78ce9bdc383cf1a299de

[danrubel, 2017-05-27 12:37:33]

danrubel@google.com changed reviewers:
+ ahe@google.com, scheglov@google.com

[danrubel, 2017-05-29 03:35:38]

Description was changed from

==========
improve fasta unterminated string recovery

* enhance handling of unterminated strings
* update ast builder and string validator to handle unterminated strings
==========

to

==========
improve fasta unterminated string recovery

* enhance handling of unterminated strings
* update ast builder and string validator to handle unterminated strings

Committed:
https://github.com/dart-lang/sdk/commit/6907345fb9323203a5cf78ce9bdc383cf1a299de
==========

[danrubel, 2017-05-29 03:35:39]

Committed patchset #1 (id:1) manually as
6907345fb9323203a5cf78ce9bdc383cf1a299de (presubmit successful).

[ahe, 2017-05-29 13:43:00]

I think this was accidentally submitted and then immediately reverted.

[danrubel, 2017-05-30 09:54:21]

On 2017/05/29 13:43:00, ahe wrote:
> I think this was accidentally submitted and then immediately reverted.

Correct. Reverted
https://github.com/dart-lang/sdk/commit/767d5ecbfd883fcfe506e67511d97f1601f42031