When metadata is not requested, elide unneeded signatures

pkg/dev_compiler/test/codegen_expected/varargs.js

Index: pkg/dev_compiler/test/codegen_expected/varargs.js
diff --git a/pkg/dev_compiler/test/codegen_expected/varargs.js b/pkg/dev_compiler/test/codegen_expected/varargs.js
index 295c642b559d9e25a927f0307f174547b2546e47..0dea1a014cf75ee27c8b68aff6ccfa4476a58aca 100644
--- a/pkg/dev_compiler/test/codegen_expected/varargs.js
+++ b/pkg/dev_compiler/test/codegen_expected/varargs.js
@@ -21,9 +21,6 @@ define(['dart_sdk'], function(dart_sdk) {
     new() {
     }
   };
-  dart.setSignature(src__varargs._Rest, {
-    constructors: () => ({new: dart.definiteFunctionType(src__varargs._Rest, [])})
-  });
   src__varargs.rest = dart.const(new src__varargs._Rest());
   src__varargs.spread = function(args) {
     dart.throw(new core.StateError('The spread function cannot be called, ' + 'it should be compiled away.'));