Fix error in postfix ++ in Crankshaft.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 56810ef6b8c16d5216a4715126f9c7558c26a8a7..d51594340303fdb1eec360f1c44157a432de9fea 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -101,6 +101,7 @@ class LChunkBuilder;
   V(EnterInlined)                              \
   V(ExternalArrayLength)                       \
   V(FixedArrayLength)                          \
+  V(ForceRepresentation)                       \
   V(FunctionLiteral)                           \
   V(GetCachedArrayIndex)                       \
   V(GlobalObject)                              \
@@ -1009,6 +1010,25 @@ class HThrow: public HUnaryOperation {
 };
 
 
+class HForceRepresentation: public HTemplateInstruction<1> {
+ public:
+  HForceRepresentation(HValue* value, Representation required_representation) {
+    SetOperandAt(0, value);
+    set_representation(required_representation);
+  }
+
+  HValue* value() { return OperandAt(0); }
+
+  virtual HValue* EnsureAndPropagateNotMinusZero(BitVector* visited);
+
+  virtual Representation RequiredInputRepresentation(int index) const {
+    return representation();  // Same as the output representation.
+  }
+
+  DECLARE_CONCRETE_INSTRUCTION(ForceRepresentation)
+};
+
+
 class HChange: public HUnaryOperation {
  public:
   HChange(HValue* value,