Implement 'displayName' for accessor and varaible elements in linker.

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

Index: pkg/analyzer/lib/src/summary/link.dart
diff --git a/pkg/analyzer/lib/src/summary/link.dart b/pkg/analyzer/lib/src/summary/link.dart
index f4486bb0e969784fc79068f47f3075497563bd13..7bfbed1de4168e81c39c01b1e95a1538e8de67d5 100644
--- a/pkg/analyzer/lib/src/summary/link.dart
+++ b/pkg/analyzer/lib/src/summary/link.dart
@@ -4351,6 +4351,9 @@ class PropertyAccessorElementForLink_Variable extends Object
   TypeInferenceNode get asTypeInferenceNode => variable._typeInferenceNode;
 
   @override
+  String get displayName => variable.displayName;
+
+  @override
   Element get enclosingElement => variable.enclosingElement;
 
   @override
@@ -5001,6 +5004,9 @@ abstract class VariableElementForLink
   }
 
   @override
+  String get displayName => unlinkedVariable.name;
+
+  @override
   PropertyAccessorElementForLink_Variable get getter =>
       _getter ??= new PropertyAccessorElementForLink_Variable(this, false);