6810861: G1: support -XX:+{PrintClassHistogram,HeapDump}{Before,After}FullGC

Summary: Call {pre,post}_full_gc_dump() before and after a STW full gc of G1CollectedHeap. Also adjusted the prefix message, including the addition of missing whitespace.
Reviewed-by: brutisso, tonyp

src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -1227,6 +1227,7 @@ bool G1CollectedHeap::do_collection(bool explicit_gc,
                        /* option      */ VerifyOption_G1UsePrevMarking);
 
     }
+    pre_full_gc_dump();
 
     COMPILER2_PRESENT(DerivedPointerTable::clear());
 
@@ -1401,6 +1402,7 @@ bool G1CollectedHeap::do_collection(bool explicit_gc,
     Universe::print_heap_after_gc();
   }
   g1mm()->update_counters();
+  post_full_gc_dump();
 
   return true;
 }

src/share/vm/gc_interface/collectedHeap.cpp

@@ -404,13 +404,13 @@ void CollectedHeap::resize_all_tlabs() {
 
 void CollectedHeap::pre_full_gc_dump() {
   if (HeapDumpBeforeFullGC) {
-    TraceTime tt("Heap Dump: ", PrintGCDetails, false, gclog_or_tty);
+    TraceTime tt("Heap Dump (before full gc): ", PrintGCDetails, false, gclog_or_tty);
     // We are doing a "major" collection and a heap dump before
     // major collection has been requested.
     HeapDumper::dump_heap();
   }
   if (PrintClassHistogramBeforeFullGC) {
-    TraceTime tt("Class Histogram: ", PrintGCDetails, true, gclog_or_tty);
+    TraceTime tt("Class Histogram (before full gc): ", PrintGCDetails, true, gclog_or_tty);
     VM_GC_HeapInspection inspector(gclog_or_tty, false /* ! full gc */, false /* ! prologue */);
     inspector.doit();
   }
@@ -418,11 +418,11 @@ void CollectedHeap::pre_full_gc_dump() {
 
 void CollectedHeap::post_full_gc_dump() {
   if (HeapDumpAfterFullGC) {
-    TraceTime tt("Heap Dump", PrintGCDetails, false, gclog_or_tty);
+    TraceTime tt("Heap Dump (after full gc): ", PrintGCDetails, false, gclog_or_tty);
     HeapDumper::dump_heap();
   }
   if (PrintClassHistogramAfterFullGC) {
-    TraceTime tt("Class Histogram", PrintGCDetails, true, gclog_or_tty);
+    TraceTime tt("Class Histogram (after full gc): ", PrintGCDetails, true, gclog_or_tty);
     VM_GC_HeapInspection inspector(gclog_or_tty, false /* ! full gc */, false /* ! prologue */);
     inspector.doit();
   }