hg: jdk/sandbox: 8221836: Avoid recalculating String.hash when zero

[chris.hegarty at oracle.com]

Changeset: 7fd299216e97
Author:    redestad
Date:      2019-04-10 12:05 +0200
URL:       http://hg.openjdk.java.net/jdk/sandbox/rev/7fd299216e97

8221836: Avoid recalculating String.hash when zero
Reviewed-by: jrose, adinn
Contributed-by: peter.levart at gmail.com, claes.redestad at oracle.com

! src/hotspot/share/classfile/javaClasses.cpp
! src/hotspot/share/classfile/javaClasses.hpp
! src/hotspot/share/classfile/javaClasses.inline.hpp
! src/hotspot/share/classfile/stringTable.cpp
! src/hotspot/share/gc/shared/stringdedup/stringDedupTable.cpp
! src/java.base/share/classes/java/lang/String.java