hg: jdk/sandbox: flatmap-branch: add initial default implementation

[julia.boes at oracle.com]

Changeset: 11206e97eb64
Author:    jboes
Date:      2020-03-09 12:05 +0000
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/11206e97eb64

flatmap-branch: add initial default implementation

! src/java.base/share/classes/java/util/stream/Stream.java
+ test/jdk/java/util/stream/test/org/openjdk/tests/java/util/stream/ConsumerFlatMapOpTest.java