[Tracing] Use TracingCategoryObserver in gc statistics

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
+#include "include/v8-tracing.h"
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
 #include "src/deoptimizer.h"
 #include "src/execution.h"
 #include "src/frames-inl.h"
 #include "src/gdb-jit.h"
 #include "src/global-handles.h"
@@ skipping 2212 matching lines @@
   while (space_it.has_next()) {
     std::unique_ptr<ObjectIterator> it(space_it.next()->GetObjectIterator());
     ObjectIterator* obj_it = it.get();
     while ((obj = obj_it->Next()) != nullptr) {
       visitor->Visit(obj);
     }
   }
 }
 
 void MarkCompactCollector::RecordObjectStats() {
-  if (FLAG_track_gc_object_stats) {
+  if (V8_UNLIKELY(FLAG_gc_stats)) {
+    heap()->CreateObjectStats();
     ObjectStatsVisitor visitor(heap(), heap()->live_object_stats_,
                                heap()->dead_object_stats_);
     VisitAllObjects(&visitor);
-    std::stringstream live, dead;
-    heap()->live_object_stats_->Dump(live);
-    heap()->dead_object_stats_->Dump(dead);
-    TRACE_EVENT_INSTANT2(TRACE_DISABLED_BY_DEFAULT("v8.gc_stats"),
-                         "V8.GC_Objects_Stats", TRACE_EVENT_SCOPE_THREAD,
-                         "live", TRACE_STR_COPY(live.str().c_str()), "dead",
-                         TRACE_STR_COPY(dead.str().c_str()));
+    if (V8_UNLIKELY(FLAG_gc_stats &
+                    v8::tracing::TracingCategoryObserver::ENABLED_BY_TRACING)) {
+      std::stringstream live, dead;
+      heap()->live_object_stats_->Dump(live);
+      heap()->dead_object_stats_->Dump(dead);
+      TRACE_EVENT_INSTANT2(TRACE_DISABLED_BY_DEFAULT("v8.gc_stats"),
+                           "V8.GC_Objects_Stats", TRACE_EVENT_SCOPE_THREAD,
+                           "live", TRACE_STR_COPY(live.str().c_str()), "dead",
+                           TRACE_STR_COPY(dead.str().c_str()));
+    }
     if (FLAG_trace_gc_object_stats) {
       heap()->live_object_stats_->PrintJSON("live");
       heap()->dead_object_stats_->PrintJSON("dead");
     }
     heap()->live_object_stats_->CheckpointObjectStats();
     heap()->dead_object_stats_->ClearObjectStats();
   }
 }
 
 void MarkCompactCollector::MarkLiveObjects() {
@@ skipping 1655 matching lines @@
       // The target is always in old space, we don't have to record the slot in
       // the old-to-new remembered set.
       DCHECK(!heap()->InNewSpace(target));
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8