Ensure that all descriptors have a valid enumeration index, and replace NextEnumIndex with LastAdde…

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 4c46dfcbb1bcbc7abe004afe21d6806fbd443e3f..4b8ca8f9927897ce15b8be4010cc531678824ba1 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -4473,7 +4473,7 @@ void MacroAssembler::CheckEnumCache(Register null_value, Label* call_runtime) {
   // Check that there is an enum cache in the non-empty instance
   // descriptors (rdx).  This is the case if the next enumeration
   // index field does not contain a smi.
-  movq(rdx, FieldOperand(rdx, DescriptorArray::kEnumerationIndexOffset));
+  movq(rdx, FieldOperand(rdx, DescriptorArray::kLastAddedOffset));
   JumpIfSmi(rdx, call_runtime);
 
   // For all objects but the receiver, check that the cache is empty.