Make Comparator fun interface in Common and JS

libraries/stdlib/js/src/kotlin/Comparator.kt

@@ -1,16 +1,12 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
 package kotlin
 
 
-public actual interface Comparator<T> {
+public actual fun interface Comparator<T> {
     @JsName("compare")
-    actual fun compare(a: T, b: T): Int
-}
-
-public actual inline fun <T> Comparator(crossinline comparison: (a: T, b: T) -> Int): Comparator<T> = object : Comparator<T> {
-    override fun compare(a: T, b: T): Int = comparison(a, b)
+    public actual fun compare(a: T, b: T): Int
 }