Implement type inference of getters/setters based on inheritance.

pkg/front_end/testcases/inference/infer_accessor_from_later_inferred_field.dart.direct.expect

Index: pkg/front_end/testcases/inference/infer_accessor_from_later_inferred_field.dart.direct.expect
diff --git a/pkg/front_end/testcases/inference/infer_accessor_from_later_inferred_field.dart.direct.expect b/pkg/front_end/testcases/inference/infer_accessor_from_later_inferred_field.dart.direct.expect
new file mode 100644
index 0000000000000000000000000000000000000000..a7caf13a9b3c5b3461a7527efff2ceedc00951c3
--- /dev/null
+++ b/pkg/front_end/testcases/inference/infer_accessor_from_later_inferred_field.dart.direct.expect
@@ -0,0 +1,21 @@
+library test;
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object implements self::B {
+  constructor •() → void
+    : super core::Object::•()
+    ;
+  get x() → dynamic
+    return self::f();
+  set x(dynamic value) → void {}
+}
+class B extends core::Object {
+  field dynamic x = 0;
+  constructor •() → void
+    : super core::Object::•()
+    ;
+}
+static method f() → dynamic
+  return null;
+static method main() → dynamic {}