JS backend: fix class object in trait #KT-4062 Fixed

js/js.tests/test/org/jetbrains/k2js/test/semantics/ClassObjectTest.java

@@ -12,6 +12,10 @@ public final class ClassObjectTest extends SingleFileTranslationTest {
         checkFooBoxIsOk();
     }
 
+    public void testInTrait() throws Exception {
+        checkFooBoxIsOk();
+    }
+
     public void testWithExtension() throws Exception {
         checkFooBoxIsOk();
     }

js/js.translator/testFiles/classObject/cases/inTrait.kt

@@ -0,0 +1,12 @@
+package foo
+
+trait A {
+    class object
+    {
+        val OK: String = "OK"
+    }
+}
+
+fun box(): String {
+    return A.OK
+}

js/js.translator/testFiles/kotlin_lib_ecma5.js

@@ -233,6 +233,7 @@ var Kotlin = {};
         obj.prototype = {};
         Object.defineProperties(obj.prototype, obj.$metadata$.properties);
         copyProperties(obj.prototype, obj.$metadata$.functions);
+        Object.defineProperty(obj, "object", {get: class_object, configurable: true});
         return obj;
     };