IR cleanup: pass deopt id as constructor argument instead of doing deopt_id_ assignment.

runtime/vm/flow_graph_builder.cc

Index: runtime/vm/flow_graph_builder.cc
diff --git a/runtime/vm/flow_graph_builder.cc b/runtime/vm/flow_graph_builder.cc
index 23f6373f1b6b4bf0223601bddeb5b69344b814d4..5ae8d6d3ec2e08ed65f7bb053eb292507355d2f3 100644
--- a/runtime/vm/flow_graph_builder.cc
+++ b/runtime/vm/flow_graph_builder.cc
@@ -1454,12 +1454,15 @@ AssertAssignableInstr* EffectGraphVisitor::BuildAssertAssignable(
                             &instantiator,
                             &instantiator_type_arguments);
   }
+
+  const intptr_t deopt_id = Isolate::Current()->GetNextDeoptId();
   return new(I) AssertAssignableInstr(token_pos,
                                       value,
                                       instantiator,
                                       instantiator_type_arguments,
                                       dst_type,
-                                      dst_name);
+                                      dst_name,
+                                      deopt_id);
 }