Remove dead code in strong mode's warnings for null literals

Remove dead code in strong mode's warnings for null literals

This code should no longer be reachable. I think it was part of our early non-null primitive type experimentation. (Currently `null` literal is treated as bottom, so it should never be a downcast if casting from null.)

R=leafp@google.com

Committed: https://github.com/dart-lang/sdk/commit/61a2bb4fdcd4f82693f2038f2eef645639970d04

[Jennifer Messerly, 2016-06-07 20:54:56]

Description was changed from

==========
Remove dead code in strong mode's warnings for null literals

This code is no longer reachable. I think it was part of our early non-null
primitive type experimentation.
==========

to

==========
Remove dead code in strong mode's warnings for null literals

This code should no longer be reachable. I think it was part of our early
non-null primitive type experimentation. (Currently `null` literal is treated as
bottom, so it should never be a downcast if casting from null.)
==========

[Jennifer Messerly, 2016-06-07 20:54:56]

jmesserly@google.com changed reviewers:
+ leafp@google.com

[Leaf, 2016-06-07 20:59:33]

lgtm

[Jennifer Messerly, 2016-06-07 21:03:35]

Description was changed from

==========
Remove dead code in strong mode's warnings for null literals

This code should no longer be reachable. I think it was part of our early
non-null primitive type experimentation. (Currently `null` literal is treated as
bottom, so it should never be a downcast if casting from null.)
==========

to

==========
Remove dead code in strong mode's warnings for null literals

This code should no longer be reachable. I think it was part of our early
non-null primitive type experimentation. (Currently `null` literal is treated as
bottom, so it should never be a downcast if casting from null.)

R=leafp@google.com

Committed:
https://github.com/dart-lang/sdk/commit/61a2bb4fdcd4f82693f2038f2eef645639970d04
==========

[Jennifer Messerly, 2016-06-07 21:03:36]

Committed patchset #1 (id:1) manually as
61a2bb4fdcd4f82693f2038f2eef645639970d04 (presubmit successful).