Move flat_buffer and api_signature into front_end.

pkg/analyzer/lib/src/summary/fasta/model.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Additional data model classes used by the summary builder.
 ///
 /// The summary builder uses 4 pieces of data:
 ///
 ///   * Unlinked**Builders: builder classes for each piece of output in the
 ///     summary (see format.dart).
 ///
 ///   * A simplified expression syntax: model relevant pieces of initializers
 ///     and constants before serializing them (see expressions.dart).
 ///
 ///   * Lazy references: a way to model references on the fly so we can build
 ///     summaries in a single pass.
 ///
 ///   * Scopes: used to track the current context of the parser, used in great
 ///     part to easily resolve lazy references at the end of the build process.
 library summary.src.scope;
 
 import 'package:analyzer/src/summary/format.dart';
 import 'package:analyzer/src/summary/idl.dart';
 
-export 'package:analyzer/src/summary/api_signature.dart';
 export 'package:analyzer/src/summary/format.dart';
 export 'package:analyzer/src/summary/idl.dart';
+export 'package:front_end/src/base/api_signature.dart';
 
 export 'expressions.dart';
 export 'visitor.dart';
 
 class ClassScope extends TypeParameterScope {
   String className;
   UnlinkedClassBuilder currentClass = new UnlinkedClassBuilder();
   UnlinkedPublicNameBuilder publicName = new UnlinkedPublicNameBuilder();
   Set<String> members = new Set<String>();
   ClassScope(Scope parent) : super(parent);
@@ skipping 143 matching lines @@
   TypeParameterScope(this.parent);
 
   void computeReference(LazyEntityRef ref) {
     var i = typeParameters.indexOf(ref.name);
     if (i < 0) return parent.computeReference(ref);
     // Note: there is no indexOffset here because we don't go into functions at
     // all (so there is no nesting of type-parameter scopes).
     ref.paramReference = typeParameters.length - i;
   }
 }