Use signature inheritance when method types are unchanged

test/browser/runtime_tests.js

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 var assert = chai.assert;
 
 suite('generic', () => {
   "use strict";
 
   let generic = dart.generic;
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     });
 
     class O extends dart.mixin(Base, M1, M2) {
       O() {};
     };
     dart.setSignature(O, {});
     var obj = new O();
     var m = dart.bind(obj, 'm');
     checkType(m, dart.functionType(core.Object, [core.int]));
     checkType(m, dart.functionType(core.int, [core.int]), false);
+
+    // Test inherited signatures
+    class P extends O {
+      P() {};
+      m(x) {return x;};
+    };
+    dart.setSignature(P, {});
+    var obj = new P();
+    var m = dart.bind(obj, 'm');
+    checkType(m, dart.functionType(core.Object, [core.int]));
+    checkType(m, dart.functionType(core.int, [core.int]), false);
   });
 
   test('Object members', () => {
     let nullHash = dart.hashCode(null);
     assert.equal(nullHash, 0);
     let nullString = dart.toString(null);
     assert.equal(nullString, 'null');
     let nullType = dart.runtimeType(null);
     assert.equal(nullType, core.Null);
 
@@ skipping 31 matching lines @@
 
 suite('primitives', function() {
   'use strict';
 
   test('fixed length list', () => {
     let list = new core.List(10);
     list[0] = 42;
     assert.throws(() => list.add(42));
   });
 });