Add flag to trace object groups

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index ad83dfb8c7e02843df2b4851d5e14e5131e1bd2d..1b6014f67218b7a53da5821c43549addb67c0691 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -828,6 +828,9 @@ void Heap::FinalizeIncrementalMarking(const char* gc_reason) {
       VMState<EXTERNAL> state(isolate_);
       HandleScope handle_scope(isolate_);
       CallGCPrologueCallbacks(kGCTypeIncrementalMarking, kNoGCCallbackFlags);
+      if (FLAG_trace_object_groups) {

[ulan, 2016/03/09 14:37:49]

Let's move it in CallGCPrologueCallbacks and we need to check for GC type so
that we don't print groups for Scavenge GCs.

[Marcel Hlopko, 2016/03/09 17:20:23]

Done.

+        isolate_->global_handles()->PrintObjectGroups();
+      }
     }
   }
   incremental_marking()->FinalizeIncrementally();
@@ -1285,6 +1288,9 @@ bool Heap::PerformGarbageCollection(
       VMState<EXTERNAL> state(isolate_);
       HandleScope handle_scope(isolate_);
       CallGCPrologueCallbacks(gc_type, kNoGCCallbackFlags);
+      if (FLAG_trace_object_groups) {

[ulan, 2016/03/09 14:37:49]

See comment above.

[Marcel Hlopko, 2016/03/09 17:20:23]

Done.

+        isolate_->global_handles()->PrintObjectGroups();
+      }
     }
   }