[turbofan] Properly implement %_ClassOf intrinsic.

src/compiler/js-intrinsic-lowering.cc

Index: src/compiler/js-intrinsic-lowering.cc
diff --git a/src/compiler/js-intrinsic-lowering.cc b/src/compiler/js-intrinsic-lowering.cc
index ab4d2b0c4badc61c381b90fa9372550122cc527f..a52da9028d6550eb3d98794aeb4712894ba23ac0 100644
--- a/src/compiler/js-intrinsic-lowering.cc
+++ b/src/compiler/js-intrinsic-lowering.cc
@@ -82,6 +82,8 @@ Reduction JSIntrinsicLowering::Reduce(Node* node) {
       return ReduceStringGetRawHashField(node);
     case Runtime::kInlineTheHole:
       return ReduceTheHole(node);
+    case Runtime::kInlineClassOf:
+      return ReduceClassOf(node);
     default:
       break;
   }
@@ -339,6 +341,13 @@ Reduction JSIntrinsicLowering::ReduceTheHole(Node* node) {
   return Replace(value);
 }
 
+Reduction JSIntrinsicLowering::ReduceClassOf(Node* node) {
+  RelaxEffectsAndControls(node);
+  node->TrimInputCount(2);
+  NodeProperties::ChangeOp(node, javascript()->ClassOf());
+  return Changed(node);
+}
+
 Reduction JSIntrinsicLowering::Change(Node* node, const Operator* op, Node* a,
                                       Node* b) {
   RelaxControls(node);