Change analysis server protocol to omit empty lists when optional.

Change analysis server protocol to omit empty lists when optional.

For object fields of type List that are marked as optional, FromJson
code automatically populates the data structure with an empty list
when the field is omitted.  ToJson code automatically omits the field
when its value is an empty list.

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

Committed: https://code.google.com/p/dart/source/detail?r=39507

[Paul Berry, 2014-08-22 14:41:25]

As discussed yesterday.

Jaime:  I'm not sure the best way to address this on the Java side so I left the
Java code generation alone.  All of the tests in com.google.dart.server_test
still pass--is this sufficient to verify that I haven't broken things too badly?

[Brian Wilkerson, 2014-08-22 15:12:45]

LGTM

https://codereview.chromium.org/482573004/diff/1/pkg/analysis_server/tool/spe...
File pkg/analysis_server/tool/spec/spec_input.html (right):

https://codereview.chromium.org/482573004/diff/1/pkg/analysis_server/tool/spe...
pkg/analysis_server/tool/spec/spec_input.html:47: will always represent empty
maps as <tt>{}</tt>.
Do we want to have the same convention for maps?

https://codereview.chromium.org/482573004/diff/1/pkg/analysis_server/tool/spe...
pkg/analysis_server/tool/spec/spec_input.html:1230: The status of the
refactoring. The array will be empty
"empty" --> "omitted"

https://codereview.chromium.org/482573004/diff/1/pkg/analysis_server/tool/spe...
pkg/analysis_server/tool/spec/spec_input.html:2823: implemented by this class.
The list will be empty if
"empty" --> "omitted"

https://codereview.chromium.org/482573004/diff/1/pkg/analysis_server/tool/spe...
pkg/analysis_server/tool/spec/spec_input.html:2831: referenced by this class.
The list will be empty if
"empty" --> "omitted"

https://codereview.chromium.org/482573004/diff/1/pkg/analysis_server/tool/spe...
pkg/analysis_server/tool/spec/spec_input.html:2839: this class. The list will be
empty if there are no
"empty" --> "omitted"

[Paul Berry, 2014-08-22 20:02:13]

PTAL.  As discussed, the new logic is now applied just to optional lists, making
the generated code now match the old handwritten code.

[scheglov, 2014-08-22 20:04:59]

LGTM

[Brian Wilkerson, 2014-08-23 17:39:53]

LGTM

[Paul Berry, 2014-08-23 18:03:45]

Committed patchset #4 manually as 39507 (presubmit successful).