Incrementally update incompletely resolved units.

Incrementally update incompletely resolved units.

When the context A uses unit U from the context B, we don't resolve U
in A to RESOLVED_UNIT, we usually stop somewhere before. But we still
want to update U in A incrementally. We don't put RESOLVED_UNITx
results into cache, so we don't write a less resolved unit as a more
resolved result.

R=brianwilkerson@google.com
BUG=

Committed: https://github.com/dart-lang/sdk/commit/da0a022962839849b3edefaffca343850339fcf6

[Brian Wilkerson, 2016-02-10 18:49:03]

LGTM

[scheglov, 2016-02-10 19:35:07]

Description was changed from

==========
Incrementally update incompletely resolved units.

When the context A uses unit U from the context B, we don't resolve U
in A to RESOLVED_UNIT, we usually stop somewhere before. But we still
want to update U in A incrementally. We don't put RESOLVED_UNITx
results into cache, so we don't write a less resolved unit as a more
resolved result.

R=brianwilkerson@google.com
BUG=
==========

to

==========
Incrementally update incompletely resolved units.

When the context A uses unit U from the context B, we don't resolve U
in A to RESOLVED_UNIT, we usually stop somewhere before. But we still
want to update U in A incrementally. We don't put RESOLVED_UNITx
results into cache, so we don't write a less resolved unit as a more
resolved result.

R=brianwilkerson@google.com
BUG=

Committed:
https://github.com/dart-lang/sdk/commit/da0a022962839849b3edefaffca343850339fcf6
==========

[scheglov, 2016-02-10 19:35:08]

Committed patchset #1 (id:1) manually as
da0a022962839849b3edefaffca343850339fcf6 (presubmit successful).