Remove ContextClass that is not needed since we're using Vectors

Remove ContextClass that is not needed since we're using Vectors

Previously reified representation of contexts, also known as
ContextClass, was used in closure conversion.  Now that we've switched
to Vectors, we no longer need that class.

R=karlklose@google.com

Committed: https://github.com/dart-lang/sdk/commit/c4f4d010fb70c6ef9cbadb0d269ed0bab814e81f

[Dmitry Stefantsov, 2017-06-15 13:24:02]

dmitryas@google.com changed reviewers:
+ kmillikin@google.com

[karlklose, 2017-06-16 07:55:51]

karlklose@google.com changed reviewers:
+ karlklose@google.com

[karlklose, 2017-06-16 07:55:52]

LGTM

[Dmitry Stefantsov, 2017-06-16 08:32:46]

Description was changed from

==========
Remove ContextClass that is not needed since we're using Vectors

Previously reified representation of contexts, also known as
ContextClass, was used in closure conversion.  Now that we've switched
to Vectors, we no longer need that class.
==========

to

==========
Remove ContextClass that is not needed since we're using Vectors

Previously reified representation of contexts, also known as
ContextClass, was used in closure conversion.  Now that we've switched
to Vectors, we no longer need that class.

R=karlklose@google.com

Committed:
https://github.com/dart-lang/sdk/commit/c4f4d010fb70c6ef9cbadb0d269ed0bab814e81f
==========

[Dmitry Stefantsov, 2017-06-16 08:32:47]

Committed patchset #2 (id:20001) manually as
c4f4d010fb70c6ef9cbadb0d269ed0bab814e81f (presubmit successful).