Look up getter in super call (issue 3621).

runtime/vm/object.h

Index: runtime/vm/object.h
===================================================================
--- runtime/vm/object.h	(revision 13373)
+++ runtime/vm/object.h	(working copy)
@@ -1326,6 +1326,11 @@
     return kind() == RawFunction::kGetterFunction;
   }
 
+  // Returns true if this function represents an implicit getter function.
+  bool IsImplicitGetterFunction() const {
+    return kind() == RawFunction::kImplicitGetter;
+  }
+
   // Returns true if this function represents an explicit setter function.
   bool IsSetterFunction() const {
     return kind() == RawFunction::kSetterFunction;