[turbofan] Lower %_DebugIsActive intrinsic.

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 6e984ff496539f5bc93813ab74fd54c44d85f662..39752bb63f86f3462db16eeb0eabe1aaf26e6b16 100644
--- a/src/compiler/js-intrinsic-lowering.h
+++ b/src/compiler/js-intrinsic-lowering.h
@@ -40,6 +40,7 @@ class V8_EXPORT_PRIVATE JSIntrinsicLowering final
 
  private:
   Reduction ReduceCreateIterResultObject(Node* node);
+  Reduction ReduceDebugIsActive(Node* node);
   Reduction ReduceDeoptimizeNow(Node* node);
   Reduction ReduceGeneratorClose(Node* node);
   Reduction ReduceGeneratorGetInputOrDebugPos(Node* node);