[turbofan] Add support for %_IsSpecObject intrinsic lowering.

src/compiler/js-intrinsic-lowering.h

Index: src/compiler/js-intrinsic-lowering.h
diff --git a/src/compiler/js-intrinsic-lowering.h b/src/compiler/js-intrinsic-lowering.h
index 8989ba19a1c46227447fe2f1c36fcbe709f028be..057f19ad413620c5a7c6068fccbb02c2ff247020 100644
--- a/src/compiler/js-intrinsic-lowering.h
+++ b/src/compiler/js-intrinsic-lowering.h
@@ -46,6 +46,7 @@ class JSIntrinsicLowering final : public AdvancedReducer {
   Reduction ReduceIncrementStatsCounter(Node* node);
   Reduction ReduceIsMinusZero(Node* node);
   Reduction ReduceIsInstanceType(Node* node, InstanceType instance_type);
+  Reduction ReduceIsSpecObject(Node* node);
   Reduction ReduceIsSmi(Node* node);
   Reduction ReduceJSValueGetValue(Node* node);
   Reduction ReduceMapGetInstanceType(Node* node);