Use off-heap data for class check instructions

runtime/vm/flow_graph.h

Index: runtime/vm/flow_graph.h
diff --git a/runtime/vm/flow_graph.h b/runtime/vm/flow_graph.h
index 5cfd9310d7724f5df5d60d820db272fcd7217616..705f6743a6004028fe20aadbfa08396b546beae9 100644
--- a/runtime/vm/flow_graph.h
+++ b/runtime/vm/flow_graph.h
@@ -133,6 +133,11 @@ class FlowGraph : public ZoneAllocated {
                                  Instruction* current,
                                  Instruction* replacement);
 
+  Instruction* CreateCheckClass(Definition* to_check,
+                                const Cids& cids,
+                                intptr_t deopt_id,
+                                TokenPosition token_pos);
+
   intptr_t current_ssa_temp_index() const { return current_ssa_temp_index_; }
   void set_current_ssa_temp_index(intptr_t index) {
     current_ssa_temp_index_ = index;