8307346: Add missing gc+phases logging for ObjectCount(AfterGC) JFR event collection code

Backport-of: 3f1927a7f3a2914402a25335c47a5a8bdd5511a6

Author: olivergillespie

src/hotspot/share/gc/g1/g1FullCollector.cpp

@@ -304,7 +304,10 @@ void G1FullCollector::phase1_mark_live_objects() {
     _heap->complete_cleaning(&_is_alive, purged_class);
   }
 
-  scope()->tracer()->report_object_count_after_gc(&_is_alive);
+  {
+    GCTraceTime(Debug, gc, phases) debug("Report Object Count", scope()->timer());
+    scope()->tracer()->report_object_count_after_gc(&_is_alive);
+  }
 }
 
 void G1FullCollector::phase2_prepare_compaction() {

src/hotspot/share/gc/parallel/psParallelCompact.cpp

@@ -2137,7 +2137,10 @@ void PSParallelCompact::marking_phase(ParCompactionManager* cm,
     JVMCI_ONLY(JVMCI::do_unloading(purged_class));
   }
 
-  _gc_tracer.report_object_count_after_gc(is_alive_closure());
+  {
+    GCTraceTime(Debug, gc, phases) tm("Report Object Count", &_gc_timer);
+    _gc_tracer.report_object_count_after_gc(is_alive_closure());
+  }
 }
 
 #ifdef ASSERT

src/hotspot/share/gc/serial/genMarkSweep.cpp

@@ -230,7 +230,10 @@ void GenMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
     JVMCI_ONLY(JVMCI::do_unloading(purged_class));
   }
 
-  gc_tracer()->report_object_count_after_gc(&is_alive);
+  {
+    GCTraceTime(Debug, gc, phases) tm_m("Report Object Count", gc_timer());
+    gc_tracer()->report_object_count_after_gc(&is_alive);
+  }
 }