Use EmbedderHeapTracer instead of object grouping when trace_embedder_heap flag is set

src/flag-definitions.h

Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index d3ee16990566c03cd0d628e1705e9f9e0b2d93f3..5b671b9cac32e422e173745c974e6c5267568db2 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -721,6 +721,10 @@ DEFINE_INT(histogram_interval, 600000,
 DEFINE_BOOL(trace_object_groups, false,
             "print object groups detected during each garbage collection")
 
+// heap.cc
+DEFINE_BOOL(trace_embedder_heap, false,
+            "use embedder heap tracing instead of object groups")
+
 // heap-snapshot-generator.cc
 DEFINE_BOOL(heap_profiler_trace_objects, false,
             "Dump heap object allocations/movements/size_updates")