Add null literals to polymer expressions

Add null literals

BUG=
R=cbracken@google.com, jmesserly@google.com

Committed: https://code.google.com/p/dart/source/detail?r=27263

[justinfagnani, 2013-09-03 21:39:33]

This is the right one :)

[Jennifer Messerly, 2013-09-03 21:47:24]

lgtm

https://codereview.chromium.org/23458017/diff/1/pkg/polymer_expressions/test/...
File pkg/polymer_expressions/test/eval_test.dart (right):

https://codereview.chromium.org/23458017/diff/1/pkg/polymer_expressions/test/...
pkg/polymer_expressions/test/eval_test.dart:171: expectEval('true && null',
false, null);
... you don't want 3-valued boolean logic here? ;) (kidding!)

[justinfagnani, 2013-09-03 21:54:35]

https://codereview.chromium.org/23458017/diff/1/pkg/polymer_expressions/test/...
File pkg/polymer_expressions/test/eval_test.dart (right):

https://codereview.chromium.org/23458017/diff/1/pkg/polymer_expressions/test/...
pkg/polymer_expressions/test/eval_test.dart:171: expectEval('true && null',
false, null);
On 2013/09/03 21:47:24, John Messerly wrote:
> ... you don't want 3-valued boolean logic here? ;) (kidding!)

don't tempt me!

[Chris Bracken, 2013-09-03 21:55:39]

lgtm

https://codereview.chromium.org/23458017/diff/1/pkg/polymer_expressions/test/...
File pkg/polymer_expressions/test/eval_test.dart (right):

https://codereview.chromium.org/23458017/diff/1/pkg/polymer_expressions/test/...
pkg/polymer_expressions/test/eval_test.dart:77: expectEval('1 == null', false);
!= test for the truly paranoid?

[justinfagnani, 2013-09-06 20:00:11]

Committed patchset #2 manually as r27263 (presubmit successful).