Implement type inference of getters/setters based on inheritance.

pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart
index 9709113adbd04a55b039830306f09c876111aaba..7630c71e5cf8096a63744be0fe88cd75a57bd228 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart
@@ -5,7 +5,7 @@
 library fasta.kernel_class_builder;
 
 import 'package:front_end/src/fasta/kernel/kernel_shadow_ast.dart'
-    show KernelField;
+    show KernelMember;
 
 import 'package:kernel/ast.dart'
     show
@@ -199,11 +199,12 @@ abstract class KernelClassBuilder
     }
     // TODO(ahe): Handle other cases: accessors, operators, and fields.
 
-    // Also record any cases where a field overrides something in a superclass,
-    // since this information will be needed for type inference.
-    if (declaredMember is KernelField &&
+    // Also record any cases where a field or getter/setter overrides something
+    // in a superclass, since this information will be needed for type
+    // inference.
+    if (declaredMember is KernelMember &&
         identical(declaredMember.enclosingClass, cls)) {
-      KernelField.recordOverride(declaredMember, interfaceMember, isSetter);
+      KernelMember.recordOverride(declaredMember, interfaceMember);
     }
   }