hg: jdk/sandbox: avoid serializing stacktraces twice

[markus.gronlund at oracle.com]

Changeset: 1b2d0f4c1e38
Author:    mgronlun
Date:      2019-08-29 14:05 +0200
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/1b2d0f4c1e38

avoid serializing stacktraces twice

! src/hotspot/share/jfr/leakprofiler/checkpoint/objectSampleCheckpoint.cpp
! src/hotspot/share/jfr/leakprofiler/checkpoint/objectSampleCheckpoint.hpp
! src/hotspot/share/jfr/leakprofiler/checkpoint/objectSampleWriter.cpp
! src/hotspot/share/jfr/recorder/stacktrace/jfrStackTraceRepository.hpp