Collection builders: specialize internal capacity helpers

(cherry picked from commit 4c26535cebaa847249e942c1d983d50fd94f2f39)

runtime/src/main/kotlin/kotlin/collections/Maps.kt

@@ -12,3 +12,21 @@ internal inline actual fun <K, V> Map<K, V>.toSingletonMapOrSelf(): Map<K, V> =
 // creates a singleton copy of map
 internal actual fun <K, V> Map<out K, V>.toSingletonMap(): Map<K, V>
         = with(entries.iterator().next()) { mutableMapOf(key to value) }
+
+
+/**
+ * Native map and set implementations do not make use of capacities or load factors.
+ */
+@PublishedApi
+internal actual fun mapCapacity(expectedSize: Int) = expectedSize
+
+/**
+ * Checks a collection builder function capacity argument.
+ * Does nothing, capacity is validated in List/Set/Map constructor
+ */
+@SinceKotlin("1.3")
+@ExperimentalStdlibApi
+@PublishedApi
+internal actual fun checkBuilderCapacity(capacity: Int) {
+    require(capacity >= 0) { "capacity must be non-negative." }
+}