Remove old frog-style dummy bodies from dart2js native class tests

tests/compiler/dart2js_native/native_call_arity3_frog_test.dart

Index: tests/compiler/dart2js_native/native_call_arity3_frog_test.dart
diff --git a/tests/compiler/dart2js_native/native_call_arity3_frog_test.dart b/tests/compiler/dart2js_native/native_call_arity3_frog_test.dart
index 0257ed903b2335f08cb674a6c664a5a31f1a1214..0adb955c526e716dca89cedd45e80c66e531054d 100644
--- a/tests/compiler/dart2js_native/native_call_arity3_frog_test.dart
+++ b/tests/compiler/dart2js_native/native_call_arity3_frog_test.dart
@@ -22,8 +22,8 @@ class B {
 // TODO(sra): Add a case where the parameters have default values.  Wait until
 // dart:html need non-null default values.
 
-A makeA() native { return new A(); }
-B makeB() native { return new B(); }
+A makeA() native;
+B makeB() native;
 
 void setup() native """
 function A() {}