Make SourceSpanException.source a getter

Make SourceSpanException.source a getter

The override in

https://github.com/dart-lang/string_scanner/blob/master/lib/src/exception.dart

is causing a problem in DDC / strong mode.

R=rnystrom@google.com

Committed: https://github.com/dart-lang/source_span/commit/32de304c1a0891941e2fdcab283abde54e748340

[vsm, 2016-02-23 00:08:42]

Description was changed from

==========
Make SourceSpanException.source a getter
==========

to

==========
Make SourceSpanException.source a getter

The override in

https://github.com/dart-lang/string_scanner/blob/master/lib/src/exception.dart

is causing a problem in DDC / strong mode.
==========

[vsm, 2016-02-23 00:08:42]

vsm@google.com changed reviewers:
+ nweiz@google.com, rnystrom@google.com

[Bob Nystrom, 2016-02-23 00:45:10]

LGTM.

[vsm, 2016-02-23 13:47:01]

Description was changed from

==========
Make SourceSpanException.source a getter

The override in

https://github.com/dart-lang/string_scanner/blob/master/lib/src/exception.dart

is causing a problem in DDC / strong mode.
==========

to

==========
Make SourceSpanException.source a getter

The override in

https://github.com/dart-lang/string_scanner/blob/master/lib/src/exception.dart

is causing a problem in DDC / strong mode.

R=rnystrom@google.com

Committed:
https://github.com/dart-lang/source_span/commit/32de304c1a0891941e2fdcab283ab...
==========

[vsm, 2016-02-23 13:47:02]

Committed patchset #1 (id:1) manually as
32de304c1a0891941e2fdcab283abde54e748340 (presubmit successful).