Track heap objects.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index a0e8ac15bff6f8a99ca45221599ab3865c07b1a3..34b784e485b3d8aa8a40e58a2cf43a78150a5b2e 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -2272,7 +2272,9 @@ LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
       needs_write_barrier_for_map) ? TempRegister() : NULL;
 
   LStoreNamedField* result = new(zone()) LStoreNamedField(obj, val, temp);
-  if (FLAG_track_fields && instr->field_representation().IsSmi()) {
+  if ((FLAG_track_fields && instr->field_representation().IsSmi()) ||
+      (FLAG_track_heap_object_fields &&
+       instr->field_representation().IsHeapObject())) {
     return AssignEnvironment(result);
   }
   return result;