Avoid allocating a whole new page for two one-element arrays when finalizing the VM isolate.

runtime/vm/clustered_snapshot.cc

Index: runtime/vm/clustered_snapshot.cc
diff --git a/runtime/vm/clustered_snapshot.cc b/runtime/vm/clustered_snapshot.cc
index 708ba428c604dd8e382f755f798521a0b8868db5..bd00047ffdd5bd3fa403a0383306bd3dfb5a6c6e 100644
--- a/runtime/vm/clustered_snapshot.cc
+++ b/runtime/vm/clustered_snapshot.cc
@@ -5302,6 +5302,10 @@ void Deserializer::ReadVMSnapshot() {
     refs_ = NULL;
   }
 
+  // Move remaining bump allocation space to the freelist so it used by C++
+  // allocations (e.g., FinalizeVMIsolate) before allocating new pages.
+  heap_->old_space()->AbandonBumpAllocation();
+
   Symbols::InitOnceFromSnapshot(isolate());
 
   Object::set_vm_isolate_snapshot_object_table(refs);