Use signature inheritance when method types are unchanged

test/codegen/expect/temps.js

Index: test/codegen/expect/temps.js
diff --git a/test/codegen/expect/temps.js b/test/codegen/expect/temps.js
index 163cdd2cee9541d0697f51ba71fa7329dc678e04..f60f0982d842a50b15f47b82bc683fca4b242d5e 100644
--- a/test/codegen/expect/temps.js
+++ b/test/codegen/expect/temps.js
@@ -12,7 +12,6 @@ var core = dart.import(core);
       this[_function] = func;
     }
   }
-  dart.setSignature(FormalCollision, {});
   let _opt = Symbol('_opt');
   class OptionalArg extends core.Object {
     OptionalArg(opt) {
@@ -26,7 +25,6 @@ var core = dart.import(core);
     }
   }
   dart.defineNamedConstructor(OptionalArg, 'named');
-  dart.setSignature(OptionalArg, {});
   function main() {
     core.print(new FormalCollision(1, 2, dart.fn(x => x)));
     core.print(new OptionalArg()[_opt]);