hg: jdk/jdk: 8243596: ModuleLayer::parents should return an unmodifiable list

[alan.bateman at oracle.com]

Changeset: ed406ec0c5cd
Author:    alanb
Date:      2020-05-07 14:44 +0100
URL:       https://hg.openjdk.java.net/jdk/jdk/rev/ed406ec0c5cd

8243596: ModuleLayer::parents should return an unmodifiable list
Reviewed-by: mchung

! src/java.base/share/classes/java/lang/ModuleLayer.java
! src/java.base/share/classes/java/lang/module/Configuration.java
! test/jdk/java/lang/ModuleLayer/BasicLayerTest.java
! test/jdk/java/lang/module/ConfigurationTest.java