Object ID Ring with tests

runtime/vm/gc_marker.cc

Index: runtime/vm/gc_marker.cc
diff --git a/runtime/vm/gc_marker.cc b/runtime/vm/gc_marker.cc
index 509f422cd9e89abf188f60e0af4e7504cff9e517..c4a7b1afe3a127e4607af8ca624d7343c4fe0453 100644
--- a/runtime/vm/gc_marker.cc
+++ b/runtime/vm/gc_marker.cc
@@ -396,6 +396,23 @@ void GCMarker::ProcessPeerReferents(PageSpace* page_space) {
 }
 
 
+void GCMarker::ProcessObjectIdTable() {
+  RawObject** table = heap_->get_object_id_ring_table();
+  const intptr_t table_size = heap_->get_object_id_ring_table_size();
+  if ((table == NULL) || (table_size <= 0)) {
+    return;
+  }
+  for (intptr_t i = 0; i < table_size; i++) {
+    RawObject* raw_obj = table[i];
+    ASSERT(raw_obj->IsHeapObject());
+    if (!raw_obj->IsMarked()) {
+      // Object has become garbage. Replace it will null.
+      table[i] = Object::null();
+    }
+  }
+}
+
+
 void GCMarker::MarkObjects(Isolate* isolate,
                            PageSpace* page_space,
                            bool invoke_api_callbacks) {
@@ -409,6 +426,7 @@ void GCMarker::MarkObjects(Isolate* isolate,
   IterateWeakRoots(isolate, &mark_weak, invoke_api_callbacks);
   mark.Finalize();
   ProcessPeerReferents(page_space);
+  ProcessObjectIdTable();
   Epilogue(isolate, invoke_api_callbacks);
 }