[es6] Fix length property of collection constructors

test/mjsunit/es6/collections.js

Index: test/mjsunit/es6/collections.js
diff --git a/test/mjsunit/es6/collections.js b/test/mjsunit/es6/collections.js
index 888b6863c199f8a943b8d2df4236ccbbccc3b50b..e1e7758b1a89e616e47c89483f1a56cd0979b677 100644
--- a/test/mjsunit/es6/collections.js
+++ b/test/mjsunit/es6/collections.js
@@ -346,7 +346,7 @@ function TestConstructor(C) {
   assertFalse(C === Object.prototype.constructor);
   assertSame(C, C.prototype.constructor);
   assertSame(C, (new C).__proto__.constructor);
-  assertEquals(1, C.length);
+  assertEquals(0, C.length);
 }
 TestConstructor(Set);
 TestConstructor(Map);