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

Index: pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart b/pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart
index 8583989de9deee06daff70a9d6b8e9096e3b2fe2..10ecedac0ec4a16bee54c707d6d95957f8d5482d 100644
--- a/pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/fasta_accessors.dart
@@ -511,7 +511,7 @@ class SendAccessor extends IncompleteSend {
             "Library prefix '${prefix.name}' can't be used with null-aware "
             "operator.\nTry removing '?'.");
       }
-      receiver = helper.scopeLookup(prefix.exports, name.name, token,
+      receiver = helper.scopeLookup(prefix.exportScope, name.name, token,
           isQualified: true, prefix: prefix);
       return helper.finishSend(receiver, arguments, offsetForToken(token));
     }
@@ -583,7 +583,7 @@ class IncompletePropertyAccessor extends IncompleteSend {
             "Library prefix '${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);
     }