Fix some out-of-line constant pool garbage collection bugs.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index b295bae9fc97b527f57bcb57b4e0d6f237a7570c..1fc74f7bc1999ccaf5a009a81f84508c0b36df8d 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -9460,7 +9460,7 @@ void ConstantPoolArray::ConstantPoolIterateBody(ObjectVisitor* v) {
   if (count_of_ptr_entries() > 0) {
     int first_ptr_offset = OffsetOfElementAt(first_ptr_index());
     int last_ptr_offset =
-        OffsetOfElementAt(first_ptr_index() + count_of_ptr_entries());
+        OffsetOfElementAt(first_ptr_index() + count_of_ptr_entries() - 1);
     v->VisitPointers(
         HeapObject::RawField(this, first_ptr_offset),
         HeapObject::RawField(this, last_ptr_offset));