JS: don't pollute object with $metadata$

#KT-8126 Fixed

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/ObjectTest.java

@@ -59,4 +59,8 @@ public final class ObjectTest extends SingleFileTranslationTest {
     public void testLambdaInObjectInsideObject() throws Exception {
         checkFooBoxIsOk();
     }
+
+    public void testDontPolluteObject() throws Exception {
+        checkFooBoxIsOk();
+    }
 }

js/js.translator/testData/kotlin_lib_ecma5.js

@@ -175,9 +175,7 @@ var Kotlin = {};
     Kotlin.createObjectNow = function (bases, constructor, functions) {
         var noNameClass = Kotlin.createClassNow(bases, constructor, functions);
         var obj = new noNameClass();
-        obj.$metadata$ = {
-            type: Kotlin.TYPE.OBJECT
-        };
+        noNameClass.$metadata$.type = Kotlin.TYPE.OBJECT;
         return  obj;
     };
 

js/js.translator/testData/object/cases/dontPolluteObject.kt

@@ -0,0 +1,45 @@
+package foo
+
+object EmptyObject {}
+
+object SomeObject {
+    val foo = 1
+    var bar = "t"
+    fun baz() {}
+}
+
+val emptyObjectExpr = object {}
+
+val someObjectExpr = object {
+    val foo = 1
+    var bar = "t"
+    fun baz() {}
+}
+
+val o = js("Object")
+
+fun keys(a: Any): List<String> {
+    val arr: Array<String> = o.keys(a)
+    return arr.toList()
+}
+
+fun getOwnPropertyNames(a: Any): List<String> {
+    val arr: Array<String> = o.getOwnPropertyNames(a)
+    return arr.toList()
+}
+
+fun box(): String {
+    assertEquals(listOf(), getOwnPropertyNames(EmptyObject))
+    assertEquals(listOf(), keys(EmptyObject))
+
+    assertEquals(listOf("foo", "bar"), getOwnPropertyNames(SomeObject))
+    assertEquals(listOf("foo", "bar"), keys(SomeObject))
+
+    assertEquals(listOf(), getOwnPropertyNames(emptyObjectExpr))
+    assertEquals(listOf(), keys(emptyObjectExpr))
+
+    assertEquals(listOf("foo", "bar"), getOwnPropertyNames(someObjectExpr))
+    assertEquals(listOf("foo", "bar"), keys(someObjectExpr))
+
+    return "OK"
+}