Implement override-based inference of instance fields.

pkg/front_end/testcases/inference/infer_final_field_getter_only.dart.outline.expect

Index: pkg/front_end/testcases/inference/infer_final_field_getter_only.dart.outline.expect
diff --git a/pkg/front_end/testcases/inference/infer_final_field_getter_only.dart.outline.expect b/pkg/front_end/testcases/inference/infer_final_field_getter_only.dart.outline.expect
new file mode 100644
index 0000000000000000000000000000000000000000..94417e6e62c6b52e325e2fae8d3c3567c1505f62
--- /dev/null
+++ b/pkg/front_end/testcases/inference/infer_final_field_getter_only.dart.outline.expect
@@ -0,0 +1,16 @@
+library test;
+import self as self;
+import "dart:core" as core;
+
+abstract class A extends core::Object {
+  constructor •() → void
+    ;
+  abstract get x() → core::int;
+}
+class B extends self::A {
+  final field dynamic x;
+  constructor •(dynamic x) → void
+    ;
+}
+static method main() → dynamic
+  ;