Use the constant pool for all constants, not just null.

runtime/vm/flow_graph.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_FLOW_GRAPH_H_
 #define VM_FLOW_GRAPH_H_
 
 #include "vm/growable_array.h"
 #include "vm/intermediate_language.h"
 #include "vm/parser.h"
@@ skipping 94 matching lines @@
   }
 
   ConstantInstr* constant_null() const {
     return constant_null_;
   }
 
   intptr_t alloc_ssa_temp_index() { return current_ssa_temp_index_++; }
 
   intptr_t InstructionCount() const;
 
-  ConstantInstr* AddConstantToInitialDefinitions(const Object& object);
+  ConstantInstr* GetConstant(const Object& object);
   void AddToInitialDefinitions(Definition* defn);
 
   void InsertBefore(Instruction* next,
                     Instruction* instr,
                     Environment* env,
                     Definition::UseKind use_kind);
   void InsertAfter(Instruction* prev,
                    Instruction* instr,
                    Environment* env,
                    Definition::UseKind use_kind);
@@ skipping 177 matching lines @@
   // Per block sets of available blocks. Block A is available at the block B if
   // and only if A dominates B and all paths from A to B are free of side
   // effects.
   GrowableArray<BitVector*> available_at_;
 };
 
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_H_