Rework how enums are implemented and reloaded

Rework how enums are implemented and reloaded

- Enum instances now hold their index and their label. Before the labels were held in a static array to the side and the index was used to look up the label.

- Before and after reload enum instances are now paired (by label) and put into the 'become' table.

Fixes https://github.com/dart-lang/sdk/issues/26877

R=rmacnak@google.com

Committed: https://github.com/dart-lang/sdk/commit/c692a64e5ad9674d2def15e85da24f71f5f40f8a

[Cutch, 2016-07-15 15:02:39]

Description was changed from

==========
Rework how enums are implemented and reloaded

BUG=
==========

to

==========
Rework how enums are implemented and reloaded

- Enum instances now hold their index and their label. Before the labels were
held in a static array to the side and the index was used to look up the label.

- Before and after reload enum instances are now paired (by label) and put into
the 'become' table.

Fixes https://github.com/dart-lang/sdk/issues/26877
==========

[Cutch, 2016-07-15 15:02:39]

johnmccutchan@google.com changed reviewers:
+ rmacnak@google.com

[rmacnak, 2016-07-15 16:59:33]

LGTM

[Cutch, 2016-07-15 17:52:24]

Description was changed from

==========
Rework how enums are implemented and reloaded

- Enum instances now hold their index and their label. Before the labels were
held in a static array to the side and the index was used to look up the label.

- Before and after reload enum instances are now paired (by label) and put into
the 'become' table.

Fixes https://github.com/dart-lang/sdk/issues/26877
==========

to

==========
Rework how enums are implemented and reloaded

- Enum instances now hold their index and their label. Before the labels were
held in a static array to the side and the index was used to look up the label.

- Before and after reload enum instances are now paired (by label) and put into
the 'become' table.

Fixes https://github.com/dart-lang/sdk/issues/26877

R=rmacnak@google.com

Committed:
https://github.com/dart-lang/sdk/commit/c692a64e5ad9674d2def15e85da24f71f5f40f8a
==========

[Cutch, 2016-07-15 17:52:25]

Committed patchset #1 (id:1) manually as
c692a64e5ad9674d2def15e85da24f71f5f40f8a (presubmit successful).