[vm] Account for pool entries that are immediate objects.

Cf. 4c82eb5

TEST=gallery
Bug: flutter/gallery#545
Change-Id: I90935aba3737f7b6873368e5a8ebf1cc48d34a22
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/250320
Commit-Queue: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Siva Annamalai <asiva@google.com>

runtime/vm/app_snapshot.cc

@@ -1988,14 +1988,12 @@ class CodeSerializationCluster : public SerializationCluster {
         // indirectly by passing the field to the runtime. A const closure
         // is a call target because its function may be called indirectly
         // via a closure call.
-        if (!only_call_targets || target->IsCode() || target->IsFunction() ||
-            target->IsField() || target->IsClosure()) {
+        intptr_t cid = target->GetClassIdMayBeSmi();
+        if (!only_call_targets || (cid == kCodeCid) || (cid == kFunctionCid) ||
+            (cid == kFieldCid) || (cid == kClosureCid)) {
           s->Push(target);
-        } else {
-          intptr_t cid = target->GetClassIdMayBeSmi();
-          if (cid >= kNumPredefinedCids) {
-            s->Push(s->isolate_group()->class_table()->At(cid));
-          }
+        } else if (cid >= kNumPredefinedCids) {
+          s->Push(s->isolate_group()->class_table()->At(cid));
         }
       }
     }