Use Future for error handling

Use Future for error handling. This appears to be the recommended way of doing things because it is safer.

R=devoncarew@google.com, scheglov@google.com

Committed: https://code.google.com/p/dart/source/detail?r=32748

[scheglov, 2014-02-18 17:08:51]

LGTM

[devoncarew, 2014-02-18 17:15:21]

lgtm

https://codereview.chromium.org/166703004/diff/1/pkg/analysis_server/lib/src/...
File pkg/analysis_server/lib/src/analysis_server.dart (right):

https://codereview.chromium.org/166703004/diff/1/pkg/analysis_server/lib/src/...
pkg/analysis_server/lib/src/analysis_server.dart:139: new
Future(performTask).catchError((exception, stackTrace) {
Does performTask() throw? I think that's the only way that the catchError
handler will be called.

[Brian Wilkerson, 2014-02-18 17:18:37]

https://codereview.chromium.org/166703004/diff/1/pkg/analysis_server/lib/src/...
File pkg/analysis_server/lib/src/analysis_server.dart (right):

https://codereview.chromium.org/166703004/diff/1/pkg/analysis_server/lib/src/...
pkg/analysis_server/lib/src/analysis_server.dart:139: new
Future(performTask).catchError((exception, stackTrace) {
> Does performTask() throw?

Not if it's working as expected, but an exception could be thrown if there's a
bug in the code somewhere. I'd rather that an exception didn't crash the server,
and this is my understanding of how to prevent that.

[Brian Wilkerson, 2014-02-18 17:20:18]

Committed patchset #1 manually as r32748 (presubmit successful).