Remove the --collect-maps flag. Maps should be always collected.

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 2ee0c2df17e0f4005694475a68e9a30ebadd9262..a27f4194587f0f8705c4ee2f938f2b92d07feef4 100644
--- a/src/heap-snapshot-generator.cc
+++ b/src/heap-snapshot-generator.cc
@@ -1294,7 +1294,7 @@ void V8HeapExplorer::ExtractMapReferences(int entry, Map* map) {
         TransitionArray::cast(raw_transitions_or_prototype_info);
     int transitions_entry = GetEntry(transitions)->index();
 
-    if (FLAG_collect_maps && map->CanTransition()) {
+    if (map->CanTransition()) {
       if (transitions->HasPrototypeTransitions()) {
         FixedArray* prototype_transitions =
             transitions->GetPrototypeTransitions();