Handle super index SendSet operations.

pkg/compiler/lib/src/resolution/access_semantics.dart

Index: pkg/compiler/lib/src/resolution/access_semantics.dart
diff --git a/pkg/compiler/lib/src/resolution/access_semantics.dart b/pkg/compiler/lib/src/resolution/access_semantics.dart
index 830d40175e87d23eefffc60dc7c34353f1331c96..834a04318f485706d8d1881999fefcedfe2a7fb2 100644
--- a/pkg/compiler/lib/src/resolution/access_semantics.dart
+++ b/pkg/compiler/lib/src/resolution/access_semantics.dart
@@ -182,7 +182,7 @@ enum CompoundAccessKind {
   /// Read from a superclass getter and write to a superclass field.
   SUPER_GETTER_FIELD,
 
-  /// Read from a superclass where the getter (and maybe setter) is unresolved.
+  /// Read from a superclass where the getter is unresolved.
   UNRESOLVED_SUPER_GETTER,
   /// Read from a superclass getter and write to an unresolved setter.
   UNRESOLVED_SUPER_SETTER,
@@ -231,6 +231,14 @@ class AccessSemantics {
 
   ConstantExpression get constant => null;
 
+  /// The element for the getter in case of a compound access,
+  /// [element] otherwise.
+  Element get getter => element;
+
+  /// The element for the setter in case of a compound access,
+  /// [element] otherwise.
+  Element get setter => element;
+
   AccessSemantics.expression()
       : kind = AccessKind.EXPRESSION;