[runtime] Introduce dedicated JSBoundFunction to represent bound functions.

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 08a69cb81bd987b464ccd729dee8907fe93ae260..7ccbf10ff36e3921ae8944ba7722863a6ae055a3 100644
--- a/src/compiler/js-intrinsic-lowering.h
+++ b/src/compiler/js-intrinsic-lowering.h
@@ -47,6 +47,7 @@ class JSIntrinsicLowering final : public AdvancedReducer {
   Reduction ReduceIncrementStatsCounter(Node* node);
   Reduction ReduceIsMinusZero(Node* node);
   Reduction ReduceIsInstanceType(Node* node, InstanceType instance_type);
+  Reduction ReduceIsFunction(Node* node);
   Reduction ReduceIsJSReceiver(Node* node);
   Reduction ReduceIsSmi(Node* node);
   Reduction ReduceJSValueGetValue(Node* node);