Remove support for object grouping during Garbage Collection

runtime/vm/scavenger.h

Index: runtime/vm/scavenger.h
diff --git a/runtime/vm/scavenger.h b/runtime/vm/scavenger.h
index af3f12932df20cb74120b9b1d77db217a046714d..11a0aa104bedeb9c8312568c53ac7d42786df7cb 100644
--- a/runtime/vm/scavenger.h
+++ b/runtime/vm/scavenger.h
@@ -231,14 +231,10 @@ class Scavenger {
   SemiSpace* Prologue(Isolate* isolate, bool invoke_api_callbacks);
   void IterateStoreBuffers(Isolate* isolate, ScavengerVisitor* visitor);
   void IterateObjectIdTable(Isolate* isolate, ScavengerVisitor* visitor);
-  void IterateRoots(Isolate* isolate,
-                    ScavengerVisitor* visitor,
-                    bool visit_prologue_weak_persistent_handles);
+  void IterateRoots(Isolate* isolate, ScavengerVisitor* visitor);
   void IterateWeakProperties(Isolate* isolate, ScavengerVisitor* visitor);
   void IterateWeakReferences(Isolate* isolate, ScavengerVisitor* visitor);
-  void IterateWeakRoots(Isolate* isolate,
-                        HandleVisitor* visitor,
-                        bool visit_prologue_weak_persistent_handles);
+  void IterateWeakRoots(Isolate* isolate, HandleVisitor* visitor);
   void ProcessToSpace(ScavengerVisitor* visitor);
   uword ProcessWeakProperty(RawWeakProperty* raw_weak,
                             ScavengerVisitor* visitor);