git: openjdk/jdk: 8263968: CDS: java/lang/ModuleLayer.EMPTY_LAYER should be singleton

[Claes Redestad]

Changeset: 133a63b4
Author:    Aleksei Voitylov <avoitylov at openjdk.org>
Committer: Claes Redestad <redestad at openjdk.org>
Date:      2021-03-24 16:32:36 +0000
URL:       https://git.openjdk.java.net/jdk/commit/133a63b4

8263968: CDS: java/lang/ModuleLayer.EMPTY_LAYER should be singleton

Reviewed-by: iklam, dholmes, alanb, redestad

! src/hotspot/share/memory/heapShared.cpp
! src/java.base/share/classes/java/lang/ModuleLayer.java
! test/hotspot/jtreg/runtime/cds/appcds/cacheObject/CheckArchivedModuleApp.java