Make sure HMathMinMax always has a supported representation

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 300673428257d9fee2d14c36757884433f50b716..4e436deea72d6dd67f9160be23505c6e74504fd6 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -3692,6 +3692,8 @@ class HMathMinMax: public HArithmeticBinaryOperation {
     return RequiredInputRepresentation(index);
   }
 
+  virtual void InferRepresentation(HInferRepresentation* h_infer);
+
   virtual Representation RepresentationFromInputs() {
     Representation left_rep = left()->representation();
     Representation right_rep = right()->representation();