Create pkg/front_end/src/base and begin populating with general use classes.

Create pkg/front_end/src/base and begin populating with general use classes.

In the long run, pkg/front_end/src/base is intended to contain code
that is useful to many components of the front end.

In this initial implementation, it contains:
- Source and the classes it references
- ErrorCode, ErrorSeverity, and ErrorType
- SyntacticEntity

Note that AnalysisTarget is included (even though strictly speaking it
is part of the analyzer task model) because it was too hard to
disentangle from Source.

Note that Token classes remain in pkg/front_end/src/scanner for now; I
plan to reorganize them at the time the parser is moved into the front
end.

R=brianwilkerson@google.com

Committed: https://github.com/dart-lang/sdk/commit/4cd9b28eb64c1eed5c24f490dee906a860eaa142

[Paul Berry, 2016-11-12 01:25:19]

paulberry@google.com changed reviewers:
+ brianwilkerson@google.com

[Brian Wilkerson, 2016-11-14 15:46:30]

lgtm

[Paul Berry, 2016-11-14 17:20:22]

Description was changed from

==========
Create pkg/front_end/src/base and begin populating with general use classes.

In the long run, pkg/front_end/src/base is intended to contain code
that is useful to many components of the front end.

In this initial implementation, it contains:
- Source and the classes it references
- ErrorCode, ErrorSeverity, and ErrorType
- SyntacticEntity

Note that AnalysisTarget is included (even though strictly speaking it
is part of the analyzer task model) because it was too hard to
disentangle from Source.

Note that Token classes remain in pkg/front_end/src/scanner for now; I
plan to reorganize them at the time the parser is moved into the front
end.
==========

to

==========
Create pkg/front_end/src/base and begin populating with general use classes.

In the long run, pkg/front_end/src/base is intended to contain code
that is useful to many components of the front end.

In this initial implementation, it contains:
- Source and the classes it references
- ErrorCode, ErrorSeverity, and ErrorType
- SyntacticEntity

Note that AnalysisTarget is included (even though strictly speaking it
is part of the analyzer task model) because it was too hard to
disentangle from Source.

Note that Token classes remain in pkg/front_end/src/scanner for now; I
plan to reorganize them at the time the parser is moved into the front
end.

R=brianwilkerson@google.com

Committed:
https://github.com/dart-lang/sdk/commit/4cd9b28eb64c1eed5c24f490dee906a860eaa142
==========

[Paul Berry, 2016-11-14 17:20:23]

Committed patchset #2 (id:20001) manually as
4cd9b28eb64c1eed5c24f490dee906a860eaa142 (presubmit successful).