implement generic method runtime behavior, fixes #301

test/codegen/expect/functions.js

 dart_library.library('functions', null, /* Imports */[
   'dart_sdk'
 ], function(exports, dart_sdk) {
   'use strict';
   const core = dart_sdk.core;
   const dart = dart_sdk.dart;
   const dartx = dart_sdk.dartx;
   const functions = Object.create(null);
   functions.bootstrap = function() {
     return dart.list([new functions.Foo()], functions.Foo);
   };
-  dart.fn(functions.bootstrap, () => dart.definiteFunctionType(core.List$(functions.Foo), []));
+  dart.lazyFn(functions.bootstrap, () => [core.List$(functions.Foo), []]);
   functions.A2B$ = dart.generic((A, B) => {
     const A2B = dart.typedef('A2B', () => dart.functionType(B, [A]));
     return A2B;
   });
   functions.A2B = functions.A2B$();
   functions.id = function(f) {
     return f;
   };
-  dart.fn(functions.id, () => dart.definiteFunctionType(functions.A2B$(functions.Foo, functions.Foo), [functions.A2B$(functions.Foo, functions.Foo)]));
+  dart.lazyFn(functions.id, () => [functions.A2B$(functions.Foo, functions.Foo), [functions.A2B$(functions.Foo, functions.Foo)]]);
   functions.Foo = class Foo extends core.Object {};
   functions.main = function() {
     core.print(functions.bootstrap()[dartx.get](0));
   };
   dart.fn(functions.main, dart.void, []);
   // Exports:
   exports.functions = functions;
 });