Reapply "Minor adjustment to usage of the ClosureClassRepresentation interface."

Reapply "Minor adjustment to usage of the ClosureClassRepresentation interface."

This reverts commit 0ee0717cc3d919bb454c5627bf35987bf11e90ad.

BUG=
R=sigmund@google.com

Committed: https://github.com/dart-lang/sdk/commit/d9c6ae343802a70ee4e3d957ea5cfcdc68759d5f

[Emily Fortuna, 2017-06-20 00:22:40]

Patchset #1 (id:1) has been deleted

[Emily Fortuna, 2017-06-20 00:23:18]

efortuna@google.com changed reviewers:
+ sigmund@google.com

[Emily Fortuna, 2017-06-20 00:23:19]

Let's try this again. I know this one is slightly more verbose than the
original, but it's getting the code ready for a bigger refactor.

[Siggi Cherem (dart-lang), 2017-06-20 00:30:22]

lgtm

https://codereview.chromium.org/2944073003/diff/20001/pkg/compiler/lib/src/js...
File pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart (right):

https://codereview.chromium.org/2944073003/diff/20001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_emitter/runtime_type_generator.dart:131: if
(closureData.isClosure && closureData.thisLocal != null) {
is closureData never null now? Will it ever be the case that isClosure is false,
but thisLocal is true? If not, we could write this as:

if (closureData?.thisLocal != null) { ... }

[Emily Fortuna, 2017-06-20 00:39:24]

Description was changed from

==========
Reapply "Minor adjustment to usage of the ClosureClassRepresentation interface."

This reverts commit 0ee0717cc3d919bb454c5627bf35987bf11e90ad.

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

to

==========
Reapply "Minor adjustment to usage of the ClosureClassRepresentation interface."

This reverts commit 0ee0717cc3d919bb454c5627bf35987bf11e90ad.

BUG=
R=sigmund@google.com

Committed:
https://github.com/dart-lang/sdk/commit/d9c6ae343802a70ee4e3d957ea5cfcdc68759d5f
==========

[Emily Fortuna, 2017-06-20 00:39:25]

Committed patchset #1 (id:20001) manually as
d9c6ae343802a70ee4e3d957ea5cfcdc68759d5f (presubmit successful).