Implement override-based type inference for instance methods.

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

 library test;
 import self as self;
 import "dart:core" as core;
 import "./infer_types_on_generic_instantiations_in_library_cycle_a.dart" as inf;
 
 abstract class A<E extends core::Object> extends core::Object implements inf::I<self::A::E> {
   final field self::A::E value = null;
   const constructor •() → void
     : super core::Object::•()
     ;
 }
 abstract class M extends core::Object {
   final field core::int y = 0;
   constructor •() → void
     : super core::Object::•()
     ;
 }
 class B<E extends core::Object> extends self::A<self::B::E> implements self::M {
   const constructor •() → void
     : super self::A::•()
     ;
   get y() → core::int
     return 0;
-  method m(dynamic a, (dynamic, core::int) → dynamic f) → dynamic {}
+  method m(dynamic a, (dynamic, core::int) → dynamic f) → self::A<self::B::E> {}
 }
 static method foo() → dynamic {
-  core::int y = new self::B::•<core::String>().{self::B::m}(null, null).value;
-  core::String z = new self::B::•<core::String>().{self::B::m}(null, null).value;
+  core::int y = new self::B::•<core::String>().{self::B::m}(null, null).{self::A::value};
+  core::String z = new self::B::•<core::String>().{self::B::m}(null, null).{self::A::value};
 }
 static method main() → dynamic {}