6797870: Add -XX:+{HeapDump,PrintClassHistogram}{Before,After}FullGC Summary: Call newly created CollectedHeap::dump_{pre,post}_full_gc before and after every stop-world full collection cycle on GenCollectedHeap and ParallelScavengeHeap. (Support for G1CollectedHeap forthcoming under CR 6810861.) Small modifications to existing heap dumping and class histogram implementation, especially to allow multiple on-the-fly histos/dumps by the VM thread during a single safepoint. Reviewed-by: jmasa, alanb, mchung

--- a/src/share/vm/services/attachListener.cpp	Fri Feb 27 15:30:47 2009 -0800
+++ b/src/share/vm/services/attachListener.cpp	Mon Mar 02 16:37:04 2009 -0800
@@ -194,7 +194,7 @@
     }
     live_objects_only = strcmp(arg0, "-live") == 0;
   }
-  VM_GC_HeapInspection heapop(out, live_objects_only /* request gc */);
+  VM_GC_HeapInspection heapop(out, live_objects_only /* request full gc */, true /* need_prologue */);
   VMThread::execute(&heapop);
   return JNI_OK;
 }