Ensure constant truncation is only done when it is safe.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 4a502ba2d46d6f552eafa84fe554df1ddaca6e5c..da6ac3f8e507c8c8be00b2c041f381fd69f4d771 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -3273,6 +3273,7 @@ class HCapturedObject V8_FINAL : public HDematerializedObject {
 };
 
 
+class HGraphBuilder;
 class HConstant V8_FINAL : public HTemplateInstruction<0> {
  public:
   DECLARE_INSTRUCTION_FACTORY_P1(HConstant, int32_t);
@@ -3379,7 +3380,8 @@ class HConstant V8_FINAL : public HTemplateInstruction<0> {
   virtual void PrintDataTo(StringStream* stream) V8_OVERRIDE;
   HConstant* CopyToRepresentation(Representation r, Zone* zone) const;
   Maybe<HConstant*> CopyToTruncatedInt32(Zone* zone);
-  Maybe<HConstant*> CopyToTruncatedNumber(Zone* zone);
+  Maybe<HConstant*> CopyToTruncatedNumberAndAdd(Zone* zone,
+                                                HGraphBuilder* builder);
   bool HasInteger32Value() const { return has_int32_value_; }
   int32_t Integer32Value() const {
     ASSERT(HasInteger32Value());