Fix exception in stack trace from issue 23348

Fix exception in stack trace from issue 23348

R=scheglov@google.com

Committed: https://code.google.com/p/dart/source/detail?r=45493

[Brian Wilkerson, 2015-05-04 15:25:04]

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

[scheglov, 2015-05-04 15:38:54]

https://codereview.chromium.org/1113063007/diff/20001/pkg/analysis_server/lib...
File pkg/analysis_server/lib/src/analysis_server.dart (right):

https://codereview.chromium.org/1113063007/diff/20001/pkg/analysis_server/lib...
pkg/analysis_server/lib/src/analysis_server.dart:447: return null;
This breaks this method's contract.

1. It promises not to return nulls.
  We need to check for "context != null" anyway, and it is easier to do just
once than first check for "pair != null" and then "context != null".

2. It promises to return a context, even if not a file is given.
   However I think that this is actually never used.

So, we can probably fix the contract and return "new ContextSourcePair(null,
null)" here.

https://codereview.chromium.org/1113063007/diff/20001/pkg/analysis_server/lib...
pkg/analysis_server/lib/src/analysis_server.dart:461: Source source = file !=
null
Now we can remove all checks of "file" for null.

[Brian Wilkerson, 2015-05-04 15:55:59]

PTAL

https://codereview.chromium.org/1113063007/diff/20001/pkg/analysis_server/lib...
File pkg/analysis_server/lib/src/analysis_server.dart (right):

https://codereview.chromium.org/1113063007/diff/20001/pkg/analysis_server/lib...
pkg/analysis_server/lib/src/analysis_server.dart:447: return null;
I misread the comment. Done.

https://codereview.chromium.org/1113063007/diff/20001/pkg/analysis_server/lib...
pkg/analysis_server/lib/src/analysis_server.dart:461: Source source = file !=
null
Done

[scheglov, 2015-05-04 16:01:02]

LGTM

[Brian Wilkerson, 2015-05-04 16:04:06]

Committed patchset #3 (id:30001) manually as 45493 (presubmit successful).