Initial support for polymorphic inlining.

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 701676786b494617a9aa58f2f867707e7db2393d..1c3a4ba901e9b0c4667d1576be73a05bbd9ea452 100644
--- a/runtime/vm/flow_graph.h
+++ b/runtime/vm/flow_graph.h
@@ -98,6 +98,7 @@ class FlowGraph : public ZoneAllocated {
 
   intptr_t max_block_id() const { return max_block_id_; }
   void set_max_block_id(intptr_t id) { max_block_id_ = id; }
+  intptr_t allocate_block_id() { return ++max_block_id_; }
 
   GraphEntryInstr* graph_entry() const {
     return graph_entry_;
@@ -146,6 +147,9 @@ class FlowGraph : public ZoneAllocated {
   void ComputeBlockEffects();
   BlockEffects* block_effects() const { return block_effects_; }
 
+  // Remove the redefinition instructions inserted to inhibit code motion.
+  void RemoveRedefinitions();
+
  private:
   friend class IfConverter;
   friend class BranchSimplifier;