[crankshaft] Refactor kAllowUndefinedAsNaN to kTruncatingToNumber.

src/crankshaft/x64/lithium-codegen-x64.cc

Index: src/crankshaft/x64/lithium-codegen-x64.cc
diff --git a/src/crankshaft/x64/lithium-codegen-x64.cc b/src/crankshaft/x64/lithium-codegen-x64.cc
index 00c989787e086bf9ce26e92da9455a17dbf238ef..923eda163982e0a1708da018bc11ed82535a18e0 100644
--- a/src/crankshaft/x64/lithium-codegen-x64.cc
+++ b/src/crankshaft/x64/lithium-codegen-x64.cc
@@ -4532,8 +4532,7 @@ void LCodeGen::DoSmiUntag(LSmiUntag* instr) {
 
 void LCodeGen::EmitNumberUntagD(LNumberUntagD* instr, Register input_reg,
                                 XMMRegister result_reg, NumberUntagDMode mode) {
-  bool can_convert_undefined_to_nan =
-      instr->hydrogen()->can_convert_undefined_to_nan();
+  bool can_convert_undefined_to_nan = instr->truncating();
   bool deoptimize_on_minus_zero = instr->hydrogen()->deoptimize_on_minus_zero();
 
   Label convert, load_smi, done;