Coalesce analysis server output messages into a single write call.

Coalesce analysis server output messages into a single write call.

This ensures that only one call to stdout.write() is made per run of
the event loop, so the output of the analysis server should not fall
behind the rate of analysis.

R=scheglov@google.com

Committed: https://code.google.com/p/dart/source/detail?r=41969

[Paul Berry, 2014-11-25 15:00:03]

paulberry@google.com changed reviewers:
+ scheglov@google.com

[Paul Berry, 2014-11-25 15:00:03]

To be applied after https://codereview.chromium.org/757013002/

[scheglov, 2014-11-25 20:00:28]

LGTM

[Paul Berry, 2014-11-25 20:39:53]

Committed patchset #1 (id:1) manually as 41969 (presubmit successful).