In summaries, don't drop unsafe prefixes.

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

Index: pkg/analyzer/lib/src/summary/resynthesize.dart
diff --git a/pkg/analyzer/lib/src/summary/resynthesize.dart b/pkg/analyzer/lib/src/summary/resynthesize.dart
index b702630a3d3a658d1960f32583c3bf8dd9ccc8f9..4f6eb205f2ac629ad52d793f599b6748cd9dd37e 100644
--- a/pkg/analyzer/lib/src/summary/resynthesize.dart
+++ b/pkg/analyzer/lib/src/summary/resynthesize.dart
@@ -440,9 +440,20 @@ class _ConstExprBuilder {
         case UnlinkedConstOperation.pushReference:
           EntityRef ref = uc.references[refPtr++];
           _ReferenceInfo info = resynthesizer.referenceInfos[ref.reference];
-          SimpleIdentifier node = AstFactory.identifier3(info.name);
-          node.staticElement = info.element;
-          _push(node);
+          if (info.enclosing != null &&
+              info.enclosing.element != null &&
+              info.enclosing.element is! ClassElement) {
+            SimpleIdentifier prefix = AstFactory.identifier3(
+                info.enclosing.name)..staticElement = info.enclosing.element;
+            SimpleIdentifier name = AstFactory.identifier3(info.name)
+              ..staticElement = info.element;
+            PrefixedIdentifier node = AstFactory.identifier(prefix, name);
+            _push(node);
+          } else {
+            SimpleIdentifier node = AstFactory.identifier3(info.name);
+            node.staticElement = info.element;
+            _push(node);
+          }
           break;
         case UnlinkedConstOperation.invokeConstructor:
           _pushInstanceCreation();