Add export dependencies to Kernel libraries and use them to resynthesize ExportElement(s) in Analyz…

pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart

 // Copyright (c) 2016, 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.
 
 library fasta.fasta_accessors;
 
 import 'package:kernel/ast.dart'
     hide InvalidExpression, InvalidInitializer, InvalidStatement;
 
 import '../../scanner/token.dart' show Token;
@@ skipping 493 matching lines @@
       return receiver.buildPropertyAccess(this, operatorOffset, isNullAware);
     }
     if (receiver is PrefixBuilder) {
       PrefixBuilder prefix = receiver;
       if (isNullAware) {
         helper.deprecated_addCompileTimeError(
             offsetForToken(token),
             "Library prefix '${prefix.name}' can't be used with null-aware "
             "operator.\nTry removing '?'.");
       }
-      receiver = helper.scopeLookup(prefix.exports, name.name, token,
+      receiver = helper.scopeLookup(prefix.exportScope, name.name, token,
           isQualified: true, prefix: prefix);
       return helper.finishSend(receiver, arguments, offsetForToken(token));
     }
     return helper.buildMethodInvocation(
         helper.toValue(receiver), name, arguments, offsetForToken(token),
         isNullAware: isNullAware);
   }
 
   Expression buildNullAwareAssignment(
       Expression value, DartType type, int offset,
@@ skipping 51 matching lines @@
       return receiver.buildPropertyAccess(this, operatorOffset, isNullAware);
     }
     if (receiver is PrefixBuilder) {
       PrefixBuilder prefix = receiver;
       if (isNullAware) {
         helper.deprecated_addCompileTimeError(
             offsetForToken(token),
             "Library prefix '${prefix.name}' can't be used with null-aware "
             "operator.\nTry removing '?'.");
       }
-      return helper.scopeLookup(prefix.exports, name.name, token,
+      return helper.scopeLookup(prefix.exportScope, name.name, token,
           isQualified: true, prefix: prefix);
     }
 
     return PropertyAccessor.make(
         helper, token, helper.toValue(receiver), name, null, null, isNullAware);
   }
 
   Expression buildNullAwareAssignment(
       Expression value, DartType type, int offset,
       {bool voidContext: false}) {
@@ skipping 460 matching lines @@
     offset ??= offsetForToken(this.token);
     return helper.throwNoSuchMethodError(new NullLiteral()..fileOffset = offset,
         plainNameForRead, arguments, offset,
         isGetter: isGetter, isSetter: isSetter);
   }
 }
 
 bool isFieldOrGetter(Member member) {
   return member is Field || (member is Procedure && member.isGetter);
 }