Make several tests running on JS backend.

compiler/testData/codegen/box/casts/mutableCollections/safeAsWithMutable.kt

@@ -1,10 +1,5 @@
-// TODO: muted automatically, investigate should it be ran for JS or not
-// IGNORE_BACKEND: JS
-
 // WITH_RUNTIME
 
-import java.util.*
-
 class Itr : Iterator<String> by ArrayList<String>().iterator()
 class MItr : MutableIterator<String> by ArrayList<String>().iterator()
 class LItr : ListIterator<String> by ArrayList<String>().listIterator()
@@ -33,6 +28,9 @@ class MME : MutableMap.MutableEntry<String, String> {
     override fun setValue(value: String): String = throw UnsupportedOperationException()
 }
 
+fun assert(condition: Boolean, message: () -> String) { if (!condition) throw AssertionError(message())}
+
+
 inline fun safeAsReturnsNull(operation: String, cast: () -> Any?) {
     try {
         val x = cast()