Free up 11 bits in fast-mode PropertyDetails by removing the enumeration-index.

src/heap-snapshot-generator.cc

Index: src/heap-snapshot-generator.cc
diff --git a/src/heap-snapshot-generator.cc b/src/heap-snapshot-generator.cc
index 3d890f720ec5aeb19d7620d7a3b7859dc27b098f..fa2c4fdf199e8505e4977bcca30dbd121a71f64c 100644
--- a/src/heap-snapshot-generator.cc
+++ b/src/heap-snapshot-generator.cc
@@ -1309,8 +1309,7 @@ void V8HeapExplorer::ExtractPropertyReferences(JSObject* js_obj, int entry) {
   if (js_obj->HasFastProperties()) {
     DescriptorArray* descs = js_obj->map()->instance_descriptors();
     int real_size = js_obj->map()->NumberOfOwnDescriptors();
-    for (int i = 0; i < descs->number_of_descriptors(); i++) {
-      if (descs->GetDetails(i).descriptor_index() > real_size) continue;
+    for (int i = 0; i < real_size; i++) {
       switch (descs->GetType(i)) {
         case FIELD: {
           int index = descs->GetFieldIndex(i);