Implement type inference of getters/setters based on inheritance.

pkg/front_end/testcases/inference/infer_setter_from_later_inferred_setter.dart.strong.expect

Index: pkg/front_end/testcases/inference/infer_setter_from_later_inferred_setter.dart.strong.expect
diff --git a/pkg/front_end/testcases/inference/infer_setter_from_later_inferred_setter.dart.strong.expect b/pkg/front_end/testcases/inference/infer_setter_from_later_inferred_setter.dart.strong.expect
new file mode 100644
index 0000000000000000000000000000000000000000..bb6ff75ead8b0c3c66266de9afb1977c2b9975dc
--- /dev/null
+++ b/pkg/front_end/testcases/inference/infer_setter_from_later_inferred_setter.dart.strong.expect
@@ -0,0 +1,23 @@
+library test;
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object implements self::B {
+  constructor •() → void
+    : super core::Object::•()
+    ;
+  set x(core::int value) → void {}
+}
+abstract class B extends core::Object implements self::C {
+  constructor •() → void
+    : super core::Object::•()
+    ;
+  abstract set x(core::int value) → void;
+}
+abstract class C extends core::Object {
+  constructor •() → void
+    : super core::Object::•()
+    ;
+  abstract set x(core::int value) → void;
+}
+static method main() → dynamic {}