hg: jdk/sandbox: 8244307: Improve assertions against taskqueue underflow

[chris.hegarty at oracle.com]

Changeset: 7fc016898ec4
Author:    kbarrett
Date:      2020-05-06 00:28 -0400
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/7fc016898ec4

8244307: Improve assertions against taskqueue underflow
Summary: Added assert_not_underflow.
Reviewed-by: tschatzl, sjohanss

! src/hotspot/share/gc/shared/taskqueue.hpp
! src/hotspot/share/gc/shared/taskqueue.inline.hpp