Create a prelinker for summaries.

pkg/analyzer/lib/src/summary/summarize_elements.dart

Index: pkg/analyzer/lib/src/summary/summarize_elements.dart
diff --git a/pkg/analyzer/lib/src/summary/summarize_elements.dart b/pkg/analyzer/lib/src/summary/summarize_elements.dart
index c47d2a0f9c3a72ed90ba1c3d000f0192e29df29c..c32b501d92901b44629998bc8939b9551b7cacc7 100644
--- a/pkg/analyzer/lib/src/summary/summarize_elements.dart
+++ b/pkg/analyzer/lib/src/summary/summarize_elements.dart
@@ -731,11 +731,13 @@ class _LibrarySerializer {
   int serializeUnresolvedReference() {
     // TODO(paulberry): in order for relinking to work, we need to record the
     // name and prefix of the unresolved symbol.  This is not (yet) encoded in
-    // the element model.
+    // the element model.  For the moment we use a name that can't possibly
+    // ever exist.
     if (unresolvedReferenceIndex == null) {
       assert(unlinkedReferences.length == prelinkedReferences.length);
       unresolvedReferenceIndex = unlinkedReferences.length;
-      unlinkedReferences.add(encodeUnlinkedReference(ctx));
+      unlinkedReferences
+          .add(encodeUnlinkedReference(ctx, name: '*unresolved*'));
       prelinkedReferences.add(encodePrelinkedReference(ctx,
           kind: PrelinkedReferenceKind.unresolved));
     }