gracefully degrade with response to client if fail to access client specified dart sdk

gracefully degrade with response to client if fail to access client specified dart sdk
+ return response if client specifies inaccessible sdk
+ cleanup JSON encode/decode references
+ cleanup channel close processing

R=brianwilkerson@google.com

Committed: https://code.google.com/p/dart/source/detail?r=33355

[Brian Wilkerson, 2014-03-05 22:48:08]

LGTM

https://codereview.chromium.org/187603010/diff/1/pkg/analysis_server/lib/src/...
File pkg/analysis_server/lib/src/domain_server.dart (right):

https://codereview.chromium.org/187603010/diff/1/pkg/analysis_server/lib/src/...
pkg/analysis_server/lib/src/domain_server.dart:116: // TODO what error code
should be returned here?
We should probably create a new error code to indicate what went wrong.
Otherwise clients can't inform their users.

[danrubel, 2014-03-05 23:27:13]

https://codereview.chromium.org/187603010/diff/1/pkg/analysis_server/lib/src/...
File pkg/analysis_server/lib/src/domain_server.dart (right):

https://codereview.chromium.org/187603010/diff/1/pkg/analysis_server/lib/src/...
pkg/analysis_server/lib/src/domain_server.dart:116: // TODO what error code
should be returned here?
On 2014/03/05 22:48:09, Brian Wilkerson wrote:
> We should probably create a new error code to indicate what went wrong.
> Otherwise clients can't inform their users.

Done.

[danrubel, 2014-03-05 23:30:49]

Committed patchset #3 manually as r33355 (presubmit successful).