Object ID Ring with tests

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
diff --git a/runtime/vm/isolate.h b/runtime/vm/isolate.h
index 27ad1ea9725c2b2d9860e7cc20865fe081b42220..d63c74c6b4816a3e5e4e7033611ed7b657a94837 100644
--- a/runtime/vm/isolate.h
+++ b/runtime/vm/isolate.h
@@ -55,6 +55,7 @@ class StubCode;
 class TypeArguments;
 class TypeParameter;
 class ObjectHistogram;
+class ObjectIdRing;
 
 
 // Used by the deoptimization infrastructure to defer allocation of unboxed
@@ -623,6 +624,11 @@ class Isolate : public BaseIsolate {
     return defer_finalization_count_ == 0;
   }
 
+  void set_object_id_ring(ObjectIdRing* ring);
+  ObjectIdRing* get_object_id_ring() {
+    return object_id_ring_;
+  }
+
  private:
   Isolate();
 
@@ -686,6 +692,9 @@ class Isolate : public BaseIsolate {
   intptr_t stack_frame_index_;
   ObjectHistogram* object_histogram_;
 
+  // Ring buffer of objects assigned an id.
+  ObjectIdRing* object_id_ring_;
+
   // Reusable handles support.
 #define REUSABLE_HANDLE_FIELDS(object)                                         \
   object* object##_handle_;                                                    \