[debug] use catch prediction flag for promise rejections.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index ec90247ba7a92bdeafdeaf454b30d2650361e57d..682a5de652e8bd8e64940f2899845985c7435167 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4860,7 +4860,11 @@ class HandlerTable : public FixedArray {
   // Conservative prediction whether a given handler will locally catch an
   // exception or cause a re-throw to outside the code boundary. Since this is
   // undecidable it is merely an approximation (e.g. useful for debugger).
-  enum CatchPrediction { UNCAUGHT, CAUGHT };
+  enum CatchPrediction {
+    UNCAUGHT,  // the handler will (likely) rethrow the exception.
+    CAUGHT,    // the exception will be caught by the handler.
+    PROMISE    // the exception will be caught and cause a promise rejection.
+  };
 
   // Getters for handler table based on ranges.
   inline int GetRangeStart(int index) const;
@@ -4915,8 +4919,8 @@ class HandlerTable : public FixedArray {
   static const int kReturnEntrySize = 2;
 
   // Encoding of the {handler} field.
-  class HandlerPredictionField : public BitField<CatchPrediction, 0, 1> {};
-  class HandlerOffsetField : public BitField<int, 1, 30> {};
+  class HandlerPredictionField : public BitField<CatchPrediction, 0, 2> {};
+  class HandlerOffsetField : public BitField<int, 2, 30> {};
 };