[JS BE] add tests for es6-classes

js/js.translator/testData/box/es6classes/primaryToSecondary.kt

@@ -0,0 +1,15 @@
+// EXPECTED_REACHABLE_NODES: 1341
+open class A(val x: Int, val y: Int) {
+    constructor(x: Int) : this(x, x)
+}
+
+class B(x: Int) : A(x)
+
+fun box(): String {
+    val b = B(45)
+
+    assertEquals(b.x, 45)
+    assertEquals(b.y, 45)
+
+    return "OK"
+}