Fix error handling in analysis.getError.

Fix error handling in analysis.getError.

Analysis.getError now has the following behaviors:

- If the file in question does not exist, or is not subject to
  analysis, a new error called GET_ERRORS_INVALID_FILE is generated.

- If the server's internal state (the set of active analysis contexts)
  changes while the query is in process, the query is transparently
  restarted; the client no longer receives a GET_ERRORS_ERROR error.

R=scheglov@google.com

Committed: https://code.google.com/p/dart/source/detail?r=39871

[Paul Berry, 2014-09-03 21:03:48]

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

[scheglov, 2014-09-03 21:24:29]

LGTM

https://codereview.chromium.org/532403002/diff/1/pkg/analysis_server/lib/src/...
File pkg/analysis_server/lib/src/analysis_server.dart (right):

https://codereview.chromium.org/532403002/diff/1/pkg/analysis_server/lib/src/...
pkg/analysis_server/lib/src/analysis_server.dart:663: Source source =
getSource(file);
// prepare Source

...just for consistency.

[Paul Berry, 2014-09-04 14:34:08]

https://codereview.chromium.org/532403002/diff/1/pkg/analysis_server/lib/src/...
File pkg/analysis_server/lib/src/analysis_server.dart (right):

https://codereview.chromium.org/532403002/diff/1/pkg/analysis_server/lib/src/...
pkg/analysis_server/lib/src/analysis_server.dart:663: Source source =
getSource(file);
On 2014/09/03 21:24:29, scheglov wrote:
> // prepare Source
> 
> ...just for consistency.

Done.

[Paul Berry, 2014-09-04 14:34:54]

Committed patchset #1 manually as 39871 (presubmit successful).