hg: jdk/sandbox: 8247681: Improve bootstrapping of unary concatenations

[chris.hegarty at oracle.com]

Changeset: 3be168f5cf1b
Author:    redestad
Date:      2020-06-17 19:36 +0200
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/3be168f5cf1b

8247681: Improve bootstrapping of unary concatenations
Reviewed-by: jlaskey, psandoz

! src/java.base/share/classes/java/lang/StringConcatHelper.java
! src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java
! test/jdk/java/lang/String/concat/ImplicitStringConcatShapes-head.template
! test/jdk/java/lang/String/concat/ImplicitStringConcatShapes.java
! test/jdk/java/lang/String/concat/StringConcatFactoryInvariants.java
! test/micro/org/openjdk/bench/java/lang/StringConcat.java