Introduce kGCCallbackForced flag.

src/heap-snapshot-generator.cc

Index: src/heap-snapshot-generator.cc
diff --git a/src/heap-snapshot-generator.cc b/src/heap-snapshot-generator.cc
index 84e819d7a6d08a1d9ec4c846b1a17952f57f80ac..f9a69df8a2a7d9f14e41bc30ac91688334768aa7 100644
--- a/src/heap-snapshot-generator.cc
+++ b/src/heap-snapshot-generator.cc
@@ -2128,7 +2128,7 @@ void NativeObjectsExplorer::FillRetainedObjects() {
     group->info = NULL;  // Acquire info object ownership.
   }
   isolate->global_handles()->RemoveObjectGroups();
-  isolate->heap()->CallGCEpilogueCallbacks(major_gc_type);
+  isolate->heap()->CallGCEpilogueCallbacks(major_gc_type, kNoGCCallbackFlags);
   // Record objects that are not in ObjectGroups, but have class ID.
   GlobalHandlesExtractor extractor(this);
   isolate->global_handles()->IterateAllRootsWithClassIds(&extractor);