RFR: Disable LeakProfiler for Shenandoah

[Zhengyu Gu]

Shenandoah crashes while processing weak references in LeakProfiler, may 
be for the same reason as ZGC(?) 
(https://bugs.openjdk.java.net/browse/JDK-8205338)

Disable it for Shenandoah as well.


diff -r 09d6d46d1f66 src/hotspot/share/jfr/leakprofiler/leakProfiler.cpp
--- a/src/hotspot/share/jfr/leakprofiler/leakProfiler.cpp       Wed Jun 
20 16:48:56 2018 -0400
+++ b/src/hotspot/share/jfr/leakprofiler/leakProfiler.cpp       Wed Jun 
20 17:57:57 2018 -0400
@@ -42,6 +42,11 @@

  static volatile jbyte suspended = 0;
  bool LeakProfiler::start(jint sample_count) {
+   if (UseShenandoahGC) {
+    log_warning(jfr)("LeakProfiler is currently not supported in 
combination with Shenandoah GC");
+    return false;
+  }
+
    if (_object_sampler != NULL) {
      // already started
      return true;


Ok?

Thanks,

-Zhengyu